Fuel Cell System

ABSTRACT

Disclosed is a fuel cell system capable of restraining a temperature change in a fuel cell caused by a refrigerant. The fuel cell system has a refrigerant circulating system for circulating the refrigerant from the fuel cell to the fuel cell. The refrigerant circulating system has flow control means for restraining the inflow of the refrigerant, which has a predetermined difference in temperature from that of the fuel cell, into the fuel cell.

TECHNICAL FIELD

The present invention relates to a fuel cell system which circulates arefrigerant to cool a fuel cell.

BACKGROUND ART

An electrochemical reaction of a fuel cell is an exothermic reaction. Tomaintain the temperature of the fuel cell at a constant level whengenerating electric power, a fuel cell system has a cooling apparatusfor the fuel cell (refer to, for example, Patent Document 1).

The cooling apparatus has a circulation passage through which arefrigerant is circulated between the fuel cell and a radiator by apump, a bypass passage for bypassing the radiator, and a thermostatvalve for switching between the radiator and the bypass passage whencirculating the refrigerant. The thermostat valve performs a switchingoperation based on the temperature of the refrigerant flowing throughthe thermostat valve. Further, the cooling apparatus houses the fuelcell, the bypass passage, and the thermostat valve in a single case soas to restrain heat dissipation of the refrigerant when the fuel cellwarms up (starts up).

Further, there has also been known a fuel cell system that uses arefrigerant that has passed through a fuel cell as a heat source for airconditioning. For instance, the fuel cell system described in PatentDocument 2 is mounted in a fuel cell car, and the exhaust heat of therefrigerant that has passed through the fuel cell is used for heatingthe interior of the car. The fuel cell system has a cooling line havinga radiator and an exhaust heat utilization line having a heater corecapable of heat-exchanging the refrigerant with air-conditioning gas, asthe lines for circulating the refrigerant to the fuel cell (refrigerantcirculation system). If there is a demand for heating the interior ofthe car, then the refrigerant flows in the cooling line and the exhaustheat utilization line. This causes the refrigerant that has passedthrough the radiator and the refrigerant that has passed through theheater core to merge and flow into the fuel cell.

[Patent Document 1] Japanese Unexamined Patent Application PublicationNo. 2004-158279 (Page 4 and FIG. 1)

[Patent Document 2] Japanese Unexamined Patent Application PublicationNo. 2001-315524 (FIG. 1)

DISCLOSURE OF INVENTION

The fuel cell system in Patent Document 1 assumes that the temperatureof the refrigerant is low when starting-up the fuel cell. Hence, whenstarting-up the fuel cell, the low-temperature refrigerant causes thethermostat valve to be switched to the bypass passage, while the pump isdriven at this time. Then, when the temperature of the refrigerant risesto a relatively high degree as the fuel cell generates electric power,the thermostat valve switches to the radiator side.

However, there is a case where the temperature of refrigerant is higheven when starting-up the fuel cell. To be more specific, in a shorttime following a stop of the fuel cell, there is a difference in theradiation amount of the refrigerant between the fuel cell inside thecase and the radiator outside the case. For this reason, a refrigerantof a relatively high temperature exists in the fuel cell, while arefrigerant of a relatively low temperature exists in the radiator.

If the fuel cell is restarted with a considerable temperature differencebetween the two, then the refrigerant of the relatively high temperaturein the fuel cell flows into the thermostat valve. This causes thethermostat valve to be undesirably switched to the radiator, leading toa possibility of a situation against original specifications.Furthermore, when the thermostat valve switches to the radiator, therefrigerant of the relatively low temperature in the radiator flows intothe fuel cell. This causes a sudden temperature change in the fuel cell.As a result, the fuel cell is subjected to a thermal shock, leading to apotential of distortion of a separator of the fuel cell.

Thus, the conventional cooling apparatus for the fuel cell has not beendesigned to implement the setting of an opening degree, including theswitching of a fluidic valve (thermostat valve), by taking a restart-upof the fuel cell into account. Furthermore, there has been a potentialof the fuel cell being adversely affected due to temperature changes,because refrigerant flows (the pump is driven) under a condition inwhich the fluidic valve is set to an out-of-specification openingdegree.

Meanwhile, the fuel cell system in Patent Document 2 circulates therefrigerant that has passed only through the cooling line into the fuelcell if there is no demand for heating. In this case, the temperature ofthe refrigerant in the exhaust heat utilization line remains unchangedand thus remains lower than the temperature of the refrigerant in thecooling line. Here, if there is a demand for heating after the operationof the fuel cell system is stopped once and then restarted, therefrigerant of the relatively low temperature in the exhaust heatutilization line flows into the fuel cell wherein the refrigerant of therelatively high temperature remains. This causes a sudden temperaturechange in the fuel cell. As a result, the fuel cell is subjected to athermal shock and hence, there has been a potential in that the fuelcell is adversely affected due to the temperature change, representedby, for example, distortion of a separator of the fuel cell or theoccurrence of flooding attributable to condensed water vapor.

It is an object of the present invention to provide a fuel cell systemcapable of restraining a temperature change in a fuel cell attributableto a refrigerant.

Specifically, an object of the present invention is to provide a fuelcell system capable of restraining the temperature change in the fuelcell attributable to the refrigerant in an exhaust heat utilization lineand to provide a fuel cell system (a cooling apparatus for a fuel cell)capable of restraining the temperature change in the fuel cell whenstarting-up the fuel cell.

To attain the aforesaid object, a fuel cell system in accordance withthe present invention is a fuel cell system provided with a refrigerantcirculating system for circulatively supplying a refrigerant to a fuelcell. The refrigerant circulating system has a flow control means forrestraining a refrigerant having a predetermined temperature differencefrom the fuel cell from flowing into the fuel cell.

This configuration restrains a refrigerant having a predeterminedtemperature difference from the fuel cell from flowing into the fuelcell, thus making it possible to restrain a temperature change in thefuel cell attributable to the refrigerant. This protects the fuel cellfrom a thermal shock.

To attain the object, a fuel cell system in accordance with the presentinvention is a fuel cell system which cools a fuel cell by circulating arefrigerant that passes through the fuel cell and which is capable ofheating air-conditioning gas in an air-conditioning line by exhaust heatof the refrigerant that has passed through the fuel cell. The fuel cellsystem includes a cooling line which has a first heat exchanger forcooling a refrigerant and circulates the refrigerant to the fuel cell;an exhaust heat utilization line which has a second heat exchanger forheat-exchanging a refrigerant with the air-conditioning gas in theair-conditioning line and which circulates the refrigerant to the fuelcell; and flow control means for controlling the flow of the refrigerantin the cooling line and the exhaust heat utilization line. The flowcontrol means starts the flow of the refrigerant in the exhaust heatutilization line after starting the flow of the refrigerant in thecooling line.

With this configuration, the flow of the refrigerant in the exhaust heatutilization line is delayed from the flow of the refrigerant in thecooling line, so that the refrigerant that is started to flow into thefuel cell is the refrigerant of the cooling line. This makes it possibleto restrain a temperature change in the fuel cell even if there is asignificant temperature difference in the refrigerant between thecooling line (fuel cell) and the exhaust heat utilization line. Inparticular, if the flow of the refrigerant in the exhaust heatutilization line is started after the flow rate of the refrigerant inthe cooling line has adequately increased, a temperature change in thefuel cell can be ideally restrained. If setting is made such that, whenstarting the flow of the refrigerant in the exhaust heat utilizationline, the flow rate thereof is gradually increased, then a temperaturechange in the fuel cell can be further ideally restrained.

Preferably, the fuel cell system further includes input means thatenables a user to input an instruction for blowing in air-conditioninggas of the air-conditioning line. The flow control means controls theflow of the refrigerant in the cooling line and the exhaust heatutilization line based on an input result of the input means.

This configuration allows the refrigerant to properly flow in thecooling line and the exhaust heat utilization line according to user'sdemand for heating.

Preferably, the flow control means starts the flow of refrigerant in thecooling line preferentially over the flow in the exhaust heatutilization line if there is an input to the input means. If there is noinput to the input means, the flow of the refrigerant in the exhaustheat utilization line may be shut off, while the refrigerant is allowedto flow in the cooling line.

With this configuration, when an input is supplied to the input means bya user to use heating, the refrigerant starts to flow in the coolingline preferentially over the exhaust heat utilization line, so that atemperature change in the fuel cell can be restrained, as describedabove. If the user does not use heating and therefore no input issupplied to the input means, then the refrigerant does not flow in theexhaust heat utilization line, so that air-conditioning gas is notheated and the fuel cell can be properly cooled by the refrigerantflowing in the cooling line.

Preferably, when starting-up the fuel cell, the flow control meansstarts the flow of the refrigerant in the exhaust heat utilization lineafter the flow of the refrigerant in the cooling line begins and allowsthe refrigerant to flow for a predetermined time in the exhaust heatutilization line even if no input is supplied to the input means.

For example, during the summer, if heating is used with a low frequencyand heating is not used for a long period of time, then the refrigerantin the exhaust heat utilization line may become stagnant therein. Thisleads to a possibility of problems, such as foreign matters building upor algae growing in the exhaust heat utilization line. According to theaforesaid construction, the refrigerant in the exhaust heat utilizationline is caused to flow once when starting-up the fuel cell, thus makingit possible to properly obviate the aforesaid problems regardless of thedemand for heating. Moreover, the timing for causing the refrigerant toflow in the exhaust heat utilization line is set to the instant the fuelcell is started up, so that the control can be simplified, as comparedwith a case where the control is carried out when operating the fuelcell.

Preferably, when starting-up the fuel cell, the flow control meansstarts the flow of the refrigerant in the exhaust heat utilization lineafter starting the flow of the refrigerant in the cooling line.

With this configuration, a temperature change in the fuel cell caused bythe refrigerant in the exhaust heat utilization line can be restrainedat a start-up (at a restart-up described above) of the fuel cell whenthe difference in refrigerant temperature between the cooling line (fuelcell) and the exhaust heat utilization line tends to increase. Inaddition, problems due to the refrigerant stagnating in the exhaust heatutilization line can be obviated with good controllability.

Preferably, the fuel cell system further includes timer means formeasuring time from a stop of the fuel cell to the next start. The flowcontrol means varies start time, at which the flow of the refrigerant inthe exhaust heat utilization line is begun when starting-up the fuelcell, on the basis of a measurement result of the timer means.

This makes it possible to vary the start time, at which the flow of therefrigerant in the exhaust heat utilization line is begun, according tothe stop time (the left-alone time at a stop) of the fuel cell. Thus,if, for example, the stop time is relatively long, then the flows of therefrigerants in the exhaust heat utilization line and the cooling linecan be simultaneously begun. If the stop time is relatively short, thenthe start of the flow of the refrigerant in the exhaust heat utilizationline can be sufficiently delayed from that in the cooling line.

According to a preferable embodiment, the fuel cell system furtherincludes a temperature sensor for detecting the temperature of arefrigerant, wherein the flow control means varies the start time, atwhich the flow of the refrigerant in the exhaust heat utilization lineis begun when starting-up the fuel cell, on the basis of a detectionresult of the temperature sensor.

With this configuration, the start time, at which the flow of therefrigerant in the exhaust heat utilization line is begun, can be variedaccording to the temperature of the refrigerant. This makes it possibleto ideally restrain a temperature change in the fuel cell. Temperaturesensors are preferably provided at a plurality of locations, e.g., inboth the cooling line and the exhaust heat utilization line.

Preferably, the flow control means causes the refrigerant to flow in atleast one of the cooling line and the exhaust heat utilization linewhile the fuel cell is being intermittently operated.

Here, the intermittent operation of the fuel cell means that the supplyof power to a load from the fuel cell is temporarily stopped and poweris supplied to the load from a secondary cell. The intermittentoperation is accomplished by intermittently (intermissively) supplyingfuel gas and oxidant gas to the fuel cell to maintain an open endvoltage of the fuel cell within a predetermined range.

The aforesaid configuration allows the refrigerant to flow through thefuel cell during the intermittent operation. In other words, thetemperature of the fuel cell can be properly controlled since the flowof the refrigerant into the fuel cell can be continued during theintermittent operation.

Preferably, the flow control means starts the flow of the refrigerant inthe cooling line preferentially over the flow in the exhaust heatutilization line when the fuel cell is intermittently operated.

With this configuration, if the refrigerant in the exhaust heatutilization line is caused to flow during the intermittent operation,then the refrigerant in the cooling line can be started to flow first.This makes it possible to ideally restrain a temperature change in thefuel cell during the intermittent operation.

Preferably, when stopping the fuel cell, the flow control means stopsthe flow in the exhaust heat utilization line preferentially over theflow of the refrigerant in the cooling line.

With this configuration, as described above, if the refrigerants in theexhaust heat utilization line and the cooling line are flowing when thefuel cell is stopped, then the flow of the refrigerant in the exhaustheat utilization line can be stopped first. This makes it possible toideally restrain a temperature change in the fuel cell at the time ofstopping.

Preferably, the flow control means includes a cooling pump forpressure-feeding a refrigerant in the cooling line, an exhaust heatutilization pump for pressure-feeding a refrigerant in the exhaust heatutilization line, and control means for controlling the driving of thecooling pump and the exhaust heat utilization pump. The control meansstarts the driving of the cooling pump and then starts the driving ofthe exhaust heat utilization pump.

This configuration includes the separate pumps for the cooling line andthe exhaust heat utilization line, thus allowing the flow of therefrigerant in each line to be properly controlled. Further, controllingthe driving start timings by coordinating the two pumps makes itpossible to start the flow of the refrigerant in the exhaust heatutilization line after starting the flow of the refrigerant in thecooling line described above.

Preferably, the control means carries out flow rate control such thatthe flow rate of the refrigerant by the cooling pump is larger than theflow rate of the refrigerant by the exhaust heat utilization pump.

This configuration allows the flow rate control by the pumps to startthe flow of the refrigerant in the exhaust heat utilization line afterthe flow rate of the refrigerant in the cooling line has sufficientlyincreased, thus permitting ideal restraint of a temperature change inthe fuel cell. This type of flow rate control includes the control ofthe number of revolutions of a pump and the control of duty ratio.

Preferably, the fuel cell system further includes a temperature sensorfor detecting the temperature of a refrigerant. The control meanscontrols the driving of the cooling pump and the exhaust heatutilization pump on the basis of a detection result of the temperaturesensor.

With this configuration, a drive condition of each pump can be changedaccording to the temperature of a refrigerant. This makes it possible tosimultaneously start the driving of the pumps if, for example, there isno temperature difference between the cooling line and the exhaust heatutilization line. Temperature sensors are preferably provided at aplurality of locations, and preferably provided on, for example, boththe cooling line and the exhaust heat utilization line.

Preferably, the exhaust heat utilization line is connected to the pointof branching from and the point of merging with the cooling line at therefrigerant outlet side of the fuel cell. The cooling line on theupstream side beyond the point of merging is provided with a check valvefor blocking the flow of the refrigerant from the point of merging tothe refrigerant outlet of the fuel cell.

This configuration makes it possible to block the refrigerant flowing inthe exhaust heat utilization line from flowing to the refrigerant outletof the fuel cell. Thus, even if the temperature of the refrigerant inthe exhaust heat utilization line is lower than the temperature of thefuel cell, the fuel cell will not be subjected to a temperature change.

According to a preferable embodiment, the flow control means includes asingle pump for pressure-feeding the refrigerant in the cooling line andthe exhaust heat utilization line, and control means for controlling thedriving of the pump. The passage resistance in the cooling line may beset to be lower than the passage resistance in the exhaust heatutilization line, so that the refrigerant of the cooling line starts toflow into the fuel cell preferentially over the refrigerant of theexhaust heat utilization line.

This configuration makes it possible to reduce the number of the pumpsby one, as compared with the configuration described above, thussimplifying the pump control by the control means. The single pumppressure-feeds the refrigerant in both the cooling line and the exhaustheat utilization line, making it possible to start the flow of therefrigerant in the cooling line preferentially over the exhaust heatutilization line by setting the passage resistances of the two lines asdescribed above.

Here, to accomplish pressure drop tuning for setting channel resistance,for example, the tube diameter of the exhaust heat utilization line maybe set to be sufficiently smaller than the tube diameter of the coolingline. Alternatively, a throttling part, such as an orifice, for makingit difficult for the refrigerant to flow through may be provided at somemidpoint in the exhaust heat utilization line.

According to a preferred embodiment, the flow control means includes asingle pump for pressure-feeding a refrigerant in the cooling line andthe exhaust heat utilization line, a switching valve for switching theflow of the refrigerant of the cooling line and the exhaust heatutilization line to the fuel cell, and control means for controlling thedriving of the pump and the switching valve. To start the flow of therefrigerant of the exhaust heat utilization line to the fuel cell, thecontrol means may switch the switching valve to the cooling line tostart the flow of the refrigerant of the cooling line to the fuel cell.

With this configuration, the flow of the refrigerant of the cooling lineto the fuel cell can be preferentially started over the exhaust heatutilization line by controlling the switching valve without depending onthe pressure drop tuning of the cooling line and the exhaust heatutilization line.

Preferably, the cooling line and the exhaust heat utilization line areprovided with confluences for merging refrigerants at a refrigerantinlet side of the fuel cell and also with branch points for splittingthe refrigerant at a refrigerant outlet side of the fuel cell.

With this configuration, the refrigerant branches at the outlet side ofthe fuel cell and flows into the cooling line and the exhaust heatutilization line and then merges again at the inlet side of the fuelcell to go into the fuel cell.

To attain the aforesaid object, another fuel cell system in accordancewith the present invention is a fuel cell system which cools a fuel cellby circulating a refrigerant that flows into the fuel cell and which iscapable of heating air-conditioning gas in an air-conditioning line byexhaust heat of the refrigerant that has passed through the fuel cell,comprising: a cooling line which has a first heat exchanger for coolinga refrigerant and circulates the refrigerant to the fuel cell; anexhaust heat utilization line which has a second heat exchanger forheat-exchanging a refrigerant with the air-conditioning gas in theair-conditioning line and which circulates the refrigerant to the fuelcell; and flow control means for controlling the flow of the refrigerantin the cooling line and the exhaust heat utilization line. The flowcontrol means carries out flow rate control such that the flow rate ofthe refrigerant of the cooling line is larger than that of the exhaustheat utilization line when the refrigerants of the cooling line and theexhaust heat utilization line are merged and moved into the fuel cell.

With this configuration, even if there is a temperature difference inrefrigerant between the cooling line (fuel cell) and the exhaust heatutilization line, the temperature of the refrigerant resulting from themerging of the refrigerants of the two lines will be close to atemperature of the refrigerant of the cooling line, since the flow rateof the refrigerant of the cooling line is larger than that of theexhaust heat utilization line. This makes it possible to restrain atemperature change in the fuel cell caused by the refrigerant of theexhaust heat utilization line even if there is a large refrigeranttemperature difference.

To attain the aforesaid object, another fuel cell system in accordancewith the present invention is a fuel cell system which cools a fuel cellby circulating a refrigerant that flows into the fuel cell and which iscapable of heating air-conditioning gas in an air-conditioning line byexhaust heat of the refrigerant that has passed through the fuel cell,comprising: a cooling line which has a first heat exchanger for coolinga refrigerant and circulates the refrigerant to the fuel cell; anexhaust heat utilization line which has a second heat exchanger forheat-exchanging the refrigerant with the air-conditioning gas in theair-conditioning line and which merges with the cooling line at arefrigerant inlet side of the fuel cell and branches from the coolingline at a refrigerant outlet side of the fuel cell; a bypass linethrough which a refrigerant flows, bypassing the fuel cell; and flowcontrol means for controlling the flow of the refrigerant in the coolingline, the exhaust heat utilization line, and the bypass line. Further,the flow control means causes the refrigerant to flow in the bypass lineto mix the refrigerants of the cooling line and the exhaust heatutilization line, then circulates the refrigerant to the fuel cell,cutting off the flow of the refrigerant in the bypass line.

With this configuration, even if there is a temperature difference inrefrigerant between the cooling line (fuel cell) and the exhaust heatutilization line, the refrigerant first flows into the bypass line,thereby mixing the refrigerants of the cooling line and the exhaust heatutilization line. Thus, the temperature of the refrigerant is leveledeven if the temperatures of the refrigerants are partly different in thecooling line and the exhaust heat utilization line. Hence, as describedabove, it is possible to restrain a temperature change in the fuel cellattributable to the refrigerant of the exhaust heat utilization line.

To attain the aforesaid object, a fuel cell system in accordance withthe present invention includes a heat exchanger for cooling arefrigerant, a circulation passage through which a refrigerant iscirculated between the heat exchanger and the fuel cell by a pump, abypass passage through which the refrigerant in the circulation passageis supplied to the fuel cell, bypassing the heat exchanger, a fluidicvalve for setting the flow of the refrigerant to the heat exchanger andthe bypass passage, and control means for controlling the fluidic valveand the pump. Further, when starting up the fuel cell, the control meanscauses the driving of the pump to be started after the opening degree ofthe fluidic valve is changed from an initial opening degree to apredetermined opening degree.

With this configuration, when starting-up the fuel cell, the openingdegree of the fluidic valve is set to the predetermined opening degreefrom the initial opening degree, and then the driving of the pump isbegun. Hence, the refrigerant to be circulated can be supplied to thefuel cell when the fluidic valve reaches an opening degree suited tospecifications, making it possible to restrain a temperature change inthe fuel cell.

Here, “after changing to the predetermined opening degree” includes acase where the driving of the pump is begun later than the change andalso a case where the driving of the pump is begun at the same time whenthe change is made.

Preferably, the fuel cell system further includes a temperature sensorfor detecting the temperature of the refrigerant. The control means setsthe fluidic valve to the predetermined opening degree on the basis of adetection result of the temperature sensor when starting-up the fuelcell.

This configuration allows the fluidic valve to be set to thepredetermined opening degree according to the temperature of therefrigerant, thus making it possible to ideally restrain a temperaturechange in the fuel cell.

Preferably, a single or a plurality of temperature sensors is providedon the circulation passage and the bypass passage, and the control meanssets the fluidic valve to the predetermined opening degree on the basisof detection results of a plurality of temperature sensors whenstarting-up the fuel cell.

With this configuration, the temperature of the refrigerant can bedetected at a plurality of positions by the plurality of temperaturesensors. This makes it possible to set the fluidic valve to thepredetermined opening degree by taking a plurality of detection resultsinto account, permitting improved controllability and reliability of thecooling apparatus.

Here, a plurality of temperature sensors may be provided, for example,at a refrigerant inlet side of the fuel cell and at a refrigerant outletside thereof, and at an upstream side of the heat exchanger and at adownstream side thereof. The temperature sensor installed at therefrigerant outlet side of the fuel cell makes it possible to ideallyreflect the temperature of the refrigerant in the fuel cell. Further,the temperature sensor installed at the downstream side of the heatexchanger makes it possible to ideally reflect the temperature of therefrigerant in the heat exchanger.

Preferably, the fuel cell system further includes a first temperaturesensor for detecting the temperature of the refrigerant in the fuel celland a second temperature sensor for detecting the temperature of therefrigerant in the heat exchanger. The control means sets the fluidicvalve to a predetermined opening degree on the basis of a temperaturedifference between a detection result by the first temperature sensorand a detection result by the second temperature sensor when starting-upthe fuel cell.

With this configuration, the fluidic valve can be set to a predeterminedopening degree on the basis of a temperature difference between therefrigerant in the fuel cell and the refrigerant in the heat exchanger.

In this case, the first temperature sensor may detect a temperature thatreflects the temperature of the refrigerant in the fuel cell. For thisreason, the first temperature sensor may be provided in the circulationpassage on the refrigerant outlet side of the fuel cell rather than inthe fuel cell. Similarly, the second temperature sensor may detect atemperature that reflects the temperature of the refrigerant in the heatexchanger. For this reason, the second temperature sensor may beprovided in the circulation passage at the downstream side of the heatexchanger rather than in the heat exchanger.

Preferably, the control means sets the fluidic valve to an openingdegree, as the predetermined opening degree of the fluidic valve, suchthat the refrigerant is allowed to flow into the bypass passage whilethe fluidic valve blocks the flow of the refrigerant into the heatexchanger at the same time if a temperature difference is a thresholdvalue or more.

With this configuration, a refrigerant of a relatively low temperaturein the heat exchanger does not have to be merged with a refrigerant of arelatively high temperature in the fuel cell if the temperaturedifference is large, so that a temperature change in the fuel cell canbe ideally restrained.

Here, “the opening degree that allows the refrigerant to flow into thebypass passage” includes not only an opening degree at which the fluidicvalve is fully opened to the bypass passage but also includes an openingdegree at which the fluidic valve is partly opened thereto.

Preferably, the predetermined opening degree is an opening degree atwhich the fluidic valve is fully opened to the bypass passage, and thecontrol means starts the driving of the pump after a zero pointadjustment for fully opening the fluidic valve when the fuel cell isstarted up.

With this configuration, the fluidic valve is fully opened to the bypasspassage preferentially over the start of the driving of the pump, and atthis time, the zero point adjustment of the fluidic valve is performed.This means that if the aforesaid temperature difference is a thresholdvalue or higher, then the refrigerant is allowed to flow only into thebypass passage, which serves also as the zero point adjustment of thefluidic valve. The zero point adjustment permits highly accurate controlof the opening degree of the fluidic valve when the fuel cell generateselectric power.

According to a preferred embodiment, the predetermined opening degree isan opening degree at which the fluidic valve allows a refrigerant toflow into at least the bypass passage.

With this configuration, when starting-up the fuel cell, the refrigerantallowed to flow at least into the bypass passage can be supplied to thefuel cell. This permits successful suppression of a temperature changein the fuel cell.

Here, “to allow a refrigerant to flow into at least the bypass passage”means a case where the refrigerant is allowed to flow into only thebypass passage or into both the bypass passage and the heat exchanger.The ratio (flow ratio) in the latter case can be set, as necessary, onthe basis of, for example, the aforesaid temperature of the refrigerant.

Preferably, the predetermined opening degree is an opening degree atwhich the fluidic valve fully opens to the heat exchanger.

This configuration securely obviates the need for supplying arefrigerant of the heat exchanger to the fuel cell when starting-up thefuel cell. Hence, a temperature change in the fuel cell can be securelyrestrained.

According to a preferred embodiment, the predetermined opening degree isan opening degree at which the fluidic valve is fully opened to thebypass passage, and the control means may start the driving of the pumpafter a zero point adjustment for fully opening the fluidic valve whenthe fuel cell is started up.

With this configuration, setting the fluidic valve so as to allow therefrigerant to circulate only to the bypass passage preferentially overthe start of the driving of the pump can also serve as the zero pointadjustment of the fluidic valve. Moreover, the zero point adjustmentpermits highly accurate control of the opening degree of the fluidicvalve when the fuel cell generates electric power.

According to a preferred embodiment, when starting-up the fuel cell, thecontrol means may change the fluidic valve to a predetermined openingdegree (i.e., an opening degree at which the fluidic valve allows therefrigerant to circulate into at least the bypass passage) after thezero point adjustment of the fluidic valve of an initial opening degree.

With this configuration, the refrigerant that has passed through atleast the bypass passage can be supplied to the fuel cell whenstarting-up the fuel cell. This permits successful suppression of atemperature change in the fuel cell. In addition, the zero pointadjustment of the fluidic valve is performed prior thereto, so that theopening degree of the fluidic valve can be controlled with high accuracywhen the fuel cell generates electric power.

Preferably, the control means sets the fluidic valve to be fully openedto the bypass passage, as the zero point adjustment of the fluidicvalve.

With this configuration, after the zero point adjustment, the fluidicvalve can be promptly set to the aforesaid predetermined opening degreeto the bypass passage.

According to a preferred embodiment, the control means sets the fluidicvalve to be fully opened to the heat exchanger, as the zero pointadjustment of the fluidic valve.

With this configuration, even if, for example, the fluidic valve failsafter the zero point adjustment, making it impossible to set the openingdegree, the refrigerant that has been cooled by the heat exchanger willbe supplied to the fuel cell when the fuel cell generates electricpower. This prevents the fuel cell from overheating. In other words,fail-safe can be accomplished.

Preferably, an initial opening degree is an opening degree at which thefluidic valve allows a refrigerant to circulate into the heat exchanger.

With this configuration, the natural heat dissipation of the refrigerantin the fuel cell can be promoted when the fuel cell is stopped.Moreover, the zero point adjustment to, for example, the heat exchangerside can be promptly accomplished. In case of a failure, such as thefluidic valve being stuck, overheating of the fuel cell can beprevented.

According to a preferred embodiment, the initial opening degree may bean opening degree at which the fluidic valve allows the refrigerant toflow into the bypass passage.

This configuration permits prompt zero point adjustment to, for example,the bypass passage.

According to a preferred embodiment, the initial opening degree may bean opening degree at which the fluidic valve allows a refrigerant tocirculate into both the heat exchanger and the bypass passage.

This configuration makes it possible to restrain overcooling andoverheating of the fuel cell which is generating electric power if thefluidic valve fails, thus allowing fail-safe to be ideally achieved.Moreover, the zero point adjustment can be promptly performed to, forexample, both the heat exchanger and the bypass passage.

Preferably, the control means sets the fluidic valve to the initialopening degree when stopping the fuel cell.

With this configuration, the fluidic valve can be appropriately set to adesired initial opening degree when the fuel cell is started up.Preferably, when the fuel cell stops, the driving of the pump is stoppedand then the fluidic valve is set to the initial opening degree.

To attain the aforesaid object, another fuel cell system in accordancewith the present invention includes a heat exchanger for cooling arefrigerant, a circulation passage through which a refrigerant iscirculated between the heat exchanger and a fuel cell by a pump, abypass passage through which the refrigerant in the circulation passageis supplied to the fuel cell to bypass the heat exchanger, a fluidicvalve for setting the circulation of the refrigerant to the heatexchanger and the bypass passage, and control means for controlling thefluidic valve and the pump. When stopping the fuel cell, the controlmeans causes the driving of the pump to be stopped and then sets thefluidic valve to a predetermined initial opening degree. In this case,the initial opening degree is preferably an opening degree at which thefluidic valve allows the refrigerant to flow into the heat exchanger.

According to these configurations, when the fuel cell is stopped, thedriving of the pump is stopped and the circulation of the refrigerant isstopped, and then the fluidic valve is set to a predetermined initialopening degree thereafter. Even if the opening degree of the fluidicvalve cannot be set due to a failure when stopping the fuel cell, therefrigerant that has been cooled by the heat exchanger is supplied tothe fuel cell when the fuel cell generates electric power, thus makingit possible to prevent the fuel cell from overheating. In other words, atemperature change in the fuel cell can be restrained and fail-safe canbe achieved.

Preferably, when starting-up the fuel cell, the control means starts thedriving of the pump after changing the fluidic valve from an initialopening degree to a predetermined opening degree.

With this configuration, when starting-up the fuel cell, the openingdegree of the fluidic valve is set to a predetermined opening degreefrom an initial opening degree and then the driving of the pump is begunthereafter. This allows the refrigerant to be supplied to the fuel cellwhen the fluidic valve has reached an opening degree suited tospecifications. Thus, when starting-up the fuel cell, a temperaturechange therein can be suppressed.

To attain the aforesaid object, another fuel cell system in accordancewith the present invention includes a heat exchanger for cooling arefrigerant, a circulation passage through which a refrigerant iscirculated between the heat exchanger and a fuel cell by a pump, abypass passage through which the refrigerant in the circulation passageis supplied to the fuel cell to bypass the heat exchanger, a fluidicvalve for setting the flow of the refrigerant to the heat exchanger andthe bypass passage, and control means for controlling the fluidic valveand the pump. When starting up the fuel cell, the control means carriesout zero point adjustment on the fluidic valve and also changes theopening degree after the zero point adjustment to a predeterminedopening degree preferentially over starting the driving of the pump.

With this configuration, when starting-up the fuel cell, the fluidicvalve is zero-point-adjusted and the opening degree thereof is set tothe predetermined opening degree, and then the driving of the pump isbegun thereafter. Thus, when the fuel cell starts up, the refrigerantcan be supplied to the fuel cell when the fluidic valve has been set toan opening degree that conforms to specifications, making it possible tosuppress a temperature change in the fuel cell. In addition, the zeropoint adjustment permits highly accurate control of the opening degreeof the fluidic valve when the fuel cell generates electric power.

Preferably, the fluidic valve is a rotary valve.

This configuration makes it possible to properly and accurately dealwith a fuel cell, which is sensitive to temperature control.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram showing the configuration of a fuelcell system according to a first embodiment.

FIG. 2 is a block diagram of the fuel cell system according to the firstembodiment.

FIG. 3 is a configuration diagram showing the configuration of a fuelcell system according to a second embodiment.

FIG. 4 is a configuration diagram showing the configuration of a fuelcell system according to a third embodiment.

FIG. 5 is a configuration diagram showing the configuration of a fuelcell system according to a fourth embodiment.

FIG. 6 is a configuration diagram showing the configuration of a fuelcell system according to a fifth embodiment.

FIG. 7 is a configuration diagram showing the configuration of a fuelcell system according to a sixth embodiment.

FIG. 8 is a configuration diagram showing the configuration of a fuelcell system according to a seventh embodiment.

FIG. 9 is a configuration diagram showing a cooling apparatus for a fuelcell provided in a fuel cell system according to an eighth embodiment.

FIG. 10 is a flowchart illustrating the processing flow of the coolingapparatus for the fuel cell according to the eighth embodiment whenstarting-up the fuel cell.

FIG. 11 is a flowchart illustrating the processing flow of the coolingapparatus for the fuel cell according to a ninth embodiment at a stop ofthe fuel cell.

FIG. 12 is a perspective view schematically showing a rotary valve as afluidic valve in a tenth embodiment.

FIGS. 13 (A) to (C) are cross-sectional diagrams schematicallyexplaining opening degrees of the rotary valve shown in FIG. 12.

FIG. 14 is a time chart of a cooling apparatus for a fuel cell accordingto an eleventh embodiment.

FIG. 15 is a time chart of a cooling apparatus for a fuel cell accordingto a twelfth embodiment.

FIG. 16 is a time chart of a cooling apparatus for a fuel cell accordingto a thirteenth embodiment.

FIG. 17 is a time chart of a cooling apparatus for a fuel cell accordingto a fourteenth embodiment.

FIG. 18 is a time chart of a cooling apparatus for a fuel cell accordingto a fifteenth embodiment.

FIG. 19 is a configuration diagram showing a cooling apparatus for afuel cell provided in a fuel cell system according to a sixteenthembodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

The following will describe fuel cell systems according to preferredembodiments of the present invention, with reference to the accompanyingdrawings. The fuel cell systems have refrigerant circulation systems forcirculatively supplying refrigerants to fuel cells. The refrigerantcirculation systems are adapted to restrain refrigerants that have apredetermined difference in temperature from the fuel cells from flowinginto the fuel cells. The following will explain fuel cell systems havingconstructions considering the utilization of exhaust heat and fuel cellsystems having constructions based on a different viewpoint from theutilization of exhaust heat.

To be more specific, in a first embodiment to a seventh embodiment (FIG.1 to FIG. 8), the fuel cell systems utilizing the exhaust heat ofrefrigerants that have cooled fuel cells will be explained. To brieflyexplain, the fuel cell systems are adapted to be mounted in fuel-cellvehicles, such as automobiles. Further, the fuel cell systems areadapted to cool fuel cells by refrigerants in main cooling lines andalso to utilize the exhaust heat of the refrigerants, which have cooledthe fuel cells, for heating, for example, the interiors of vehicles. Thefuel cell systems in accordance with the present invention arecharacterized in that the flows of refrigerants in cooling lines and inexhaust heat utilization lines are controlled so as not to cause thermalshocks to the fuel cells attributable to low-temperature refrigerants inthe exhaust heat utilization lines.

In an eighth embodiment to a sixteenth embodiment (FIG. 9 to FIG. 19),other fuel cell systems giving considerations to a different aspect fromthe utilization of exhaust heat will be explained. Briefly speaking, thefuel cell systems have cooling apparatuses of fuel cells, and thecooling apparatuses lower the temperatures of the fuel cells caused bygeneration of electric power and control the temperatures of the fuelcells during the generation of electric power. The fuel cell systems inaccordance with the present invention are characterized primarily bypredetermined control carried out on fluidic valves and pumps in thecooling apparatuses of the fuel cells, thereby ideally restrainingtemperature changes in the fuel cells when the fuel cells are started up(warmed up).

FIRST EMBODIMENT

FIG. 1 is a system diagram showing a cooling system of a fuel cellsystem.

A fuel cell system 1 has a fuel cell 2 of a stack structure having alaminate of multiple unit cells, which are basic units, and a controller3 (refer to FIG. 2) which overall controls the entire system. A stackcase 5 houses the fuel cell 2 together with peripheral detecting devicesand the like. The stack case 5 is formed of a metal or hard resinmaterial and fixed to the bottom of the floor or the like of a vehicleinterior through the intermediary of a bracket or the like. Hydrogen gasas fuel gas and air as oxidant gas are supplied to the fuel cell 2through piping lines, which are not shown. The fuel cell 2 generateselectric power by an electrochemical reaction of these two gases andalso generates heat.

The fuel cell 2 comes in a plurality of types, including aphosphoric-acid type; the fuel cell in the present embodiment iscomposed of a solid polymer electrolytic type, which is ideally suitedfor installation in a vehicle. Although not shown, a unit cell of thefuel cell 2 is formed by an MEA (Membrane Electrode Assembly) sandwichedbetween a pair of separators made of a metal or the like. As inner flowpassages in the stack-structured fuel cell 2, a flow passage of fuelgas, a flow passage of oxidant gas, and a flow passage of cooling waterare provided. These flow passages are formed primarily in the planes ofthe separators. The fuel cell 2 is cooled by the cooling water servingas a refrigerant passed through the inner flow passages for the coolingwater.

The fuel cell system 1 has a cooling line 10 shown on the left in thefigure and an exhaust heat utilization line 11 on the right in thefigure, as the lines for circulating the cooling water (a refrigerantcirculation system) to the fuel cell 2. The cooling line 10 and theexhaust heat utilization line 11 are provided with a confluence 13 formerging the cooling water at a cooling water inlet 2 a of the fuel cell2 and a branch point 14 for splitting the cooling water at a coolingwater outlet 2 b of the fuel cell 2. The confluence 13 and the branchpoint 14 may be provided with valves, such as three-way valves, so as tomake it possible to block the merging of the cooling water at theconfluence 13 or to branch the cooling water only in one way at thebranch point 14.

The cooling line 10 has a radiator 21 for cooling the cooling waterdischarged from the fuel cell 2, a bypass passage 22 for bypassing theradiator 21, a cooling pump 23 for pressure-feeding the cooling water inthe cooling line 10, and a switching valve 24 for setting the flow ofthe cooling water to the radiator 21 and the bypass passage 22. Thecooling line 10 is formed primarily of a first passage 31 from thecooling water outlet 2 b of the fuel cell 2 to an inlet of the radiator21, a second passage 32 from an outlet of the radiator 21 to a firstport 24 a of the switching valve 24, and a third passage 33 from asecond port 24 b of the switching valve 24 to the cooling water inlet 2a of the fuel cell 2.

The radiator 21 (a first heat exchanger) has therein a passage thatleads the cooling water whose temperature has risen due to an electricgeneration reaction of the fuel cell 2, and the cooling water isheat-exchanged (heat-dissipated) with outside air by passing through thepassage in the radiator 21. The radiator 21 is provided, for example, onthe front of a vehicle. The radiator 21 is also provided with a fan 26for blowing outside air to the internal passage. The fan 26 acceleratesthe cooling of the cooling water in the radiator 21. The fan 26 isconnected to the controller 3 and the driving thereof is controlled bythe controller 3.

The bypass passage 22 has a upstream end connected to the downstream endof the cooling pump 23 of the first passage 31, and a downstream endconnected to a third port 24 c of the switching valve 24. The bypasspassage 22 has no auxiliary device having a cooling effect.

The cooling pump 23 is connected to the controller 3 and the drivingthereof is controlled by the controller 3. When the driving of thecooling pump 23 is begun, the cooling water in the cooling line 10 flowsto maintain the temperature of the fuel cell 2 within a predeterminedrange. Then, when the driving of the cooling pump 23 is stopped, theflow of the cooling water in the cooling line 10 is stopped. Note, thecooling pump 23 positioned on the upstream side of the radiator 21 maybe of course positioned on the downstream side of the radiator 21 or theswitching valve 24.

The switching valve 24 has a three-way vale structure having the firstport 24 a, the second port 24 b, and the third port 24 c. The switchingvalve 24 is formed of, for example, a rotary valve, and configured so asto switch the cooling water to one of the radiator 21 and the bypasspassage 22 or to both thereof.

For instance, if the switching valve 24 is changed over to the radiator21, then the cooling line 10 functions as a circulation passage forcirculating the cooling water between the radiator 21 and the fuel cell2. Meanwhile, if the switching valve 24 is changed over to the bypasspassage 22, the cooling line 10 functions as a circulation passage forcirculatively supplying the cooling water to the fuel cell 2 to bypassthe radiator 21. In this case, the cooling water that is not subjectedto the heat dissipation effect by the radiator 21 flows into the fuelcell 2.

The switching valve 24 is configured to permit the adjustment of theopening degree of the valve so as to permit the adjustment of the inflowrate of the cooling water into the radiator 21 and the bypass passage22. The switching valve 24 is connected to the controller 3, and theopening degree of the valve, including a switching operation, iscontrolled by output signals from the controller 3. This type ofswitching valve 24 may be composed of, for example, an electromagneticvalve type driven by a solenoid, a motor-operated valve type driven by amotor, or a type driven by electric/magnetic forces of a piezoelectricelement, a magnetostrictive element or the like.

The exhaust heat utilization line 11 has a heater core 41 (a second heatexchanger) for heat-exchanging the cooling water discharged from thefuel cell 2 with an air-conditioning gas, and an exhaust heatutilization pump 42 for pressure-feeding the cooling water of theexhaust heat utilization line 11. The exhaust heat utilization line 11is a line that utilizes the exhaust heat of the cooling water dischargedfrom the fuel cell 2 to cool the cooling water by heatingair-conditioning gas, and functions as a circulation passage forcirculating the cooling water between the heater core 41 and the fuelcell 2.

The exhaust heat utilization pump 42 is connected to the controller 3,and the driving thereof is controlled by the controller 3. As will bedescribed later, the exhaust heat utilization pump 42 is controlled incooperation with the cooling pump 23. When the driving of the exhaustheat utilization pump 42 is begun, the cooling water in the exhaust heatutilization line 11 flows and the cooling water that has beenheat-exchanged in the heater core 41 flows into the fuel cell 2. Then,when the driving of the exhaust heat utilization pump 42 is stopped, theflow of the cooling water in the exhaust heat utilization line 11 isstopped. Note, the exhaust heat utilization pump 42, which has beenpositioned on the upstream side of the heater core 41, may be of coursepositioned on the downstream side of the heater core 41.

The heater core 41 is mounted, for example, on the front of a vehicle,as with the radiator 21. The heater core 41 has therein a passage thatleads the cooling water whose temperature has risen due to an electricgeneration reaction of the fuel cell 2, and the cooling water isheat-exchanged (heat-dissipated) with air-conditioning gas by passingthrough the passage in the heater core 41. Hence, the heater core 41 isdisposed in an air-conditioning line 51 (duct) in an air conditioner 50that provides a passage for the air-conditioning gas.

The air conditioner 50 takes in, for example, the air in a vehicle(internal air) or the air outside the vehicle (outside air), conditionsthe air and blows the conditioned air into the vehicle. The airconditioner 50 has, although not shown, an evaporator provided on theupstream side of the heater core 41 in the air-conditioning line 51 anda blower, which is provided on the upstream side of the evaporator andpressure-feeds air-conditioning gas to the heater core 41. For example,a blowout port, through which air-conditioning gas is supplied into avehicle, is provided at the bottommost downstream of theair-conditioning line 51.

The air conditioner 50 has an input means 52, such as a switch, whichenables a user to perform an input operation (refer to FIG. 2). Theinput means 52 enables the user to give instructions on the execution ofblowing air conditioning gas of the air conditioning line 51. Morespecifically, when the input means 52 receives an input, the airconditioner 50 performs warming up. At this time, the cooling waterflows into both the cooling line 10 and the exhaust heat utilizationline 11, and the air conditioning gas that has been heated by the heatercore 41 is supplied into the vehicle. Meanwhile, if no input is suppliedto the input means 52, then the air conditioner 50 is not actuated andthe supply of the air conditioning gas into the vehicle is shut off, thecooling water flowing only in the cooling line 10. Note, anconfiguration may be made such that the air conditioner 50 can beswitched to a cooling operation by the input means 52.

The cooling line 10 and the exhaust heat utilization line 11 areprovided with a plurality of temperature sensors 61-65 along the linesin a scattered manner. To be more specific, there are provided atemperature sensor 61 on the downstream side of the radiator 21, atemperature sensor 62 on the bypass passage 22, a temperature sensor 63at the cooling water inlet 2 a of the fuel cell 2, a temperature sensor64 at the cooling water outlet 2 b thereof, and a temperature sensor 65at the downstream side of the heater core 41. The temperature sensors 63and 64 near the cooling water inlet 2 a and the cooling water outlet 2 bof the fuel cell 2 are housed in the stack case 5. However, thesetemperature sensors 63 and 64 may be provided outside the stack case 5.

The temperature sensor 61 at the downstream side of the radiator 21detects a temperature that reflects the temperature of the cooling waterat the outlet of the radiator 21. Further, the temperature sensor 64 atthe cooling water outlet 2 b detects a temperature that reflects thetemperature of the cooling water in the fuel cell 2. The temperaturesensor 65 at the downstream side of the heater core 41 detects atemperature that reflects the temperature of the cooling water that haspassed through the heater core 41. These plural temperature sensors 61to 65 are connected to the controller 3, and supply their detectionresults to the controller 3.

FIG. 2 is a block diagram showing a control configuration of the fuelcell system 1. The controller 3 (ECU) has a CPU, a ROM storing controlprograms and control data to be processed by the CPU, a RAM used asvarious work areas mainly for control processing, and an input/outputinterface, none of which are shown. These are connected with each otherthrough the intermediary of buses.

Connected to the input/output interface are various types of sensors,including a plurality of temperature sensors 61 to 65, and the inputmeans 52 in the air conditioner 50 in addition to various types ofdrivers for driving the cooling pump 23, the switching valve 24, theexhaust heat utilization pump 42, and the like. The controller 3functions as a flow control means that works in cooperation with thecooling pump 23 and the exhaust heat utilization pump 42 to control theflow of the cooling water in the cooling line 10 and the exhaust heatutilization line 11. The flow control means restrains the cooling waterthat has a predetermined temperature difference from the fuel cell 2from flowing into the fuel cell 2, as will be discussed hereinafter.

According to a control program in the ROM, the CPU receives detectionsignals of the temperature sensors 61 to 65 and the like and inputsignals of the input means 52 through the intermediary of theinput/output interface, processes various types of data and the like inthe RAM and then outputs control signals to the various drivers throughthe intermediary of the input/output interface, thereby integrallycontrolling the entire fuel cell system 1, including the cooperativecontrol of the cooling pump 23 and the exhaust heat utilization pump 42.

As described above, if there is no demand of heating the interior of thevehicle while the fuel cell system 1 is in operation, then the coolingwater flows only in the cooling line 10. Thus, the cooling waterretained in the exhaust heat utilization line 11 has a lowertemperature, as compared with the cooling water in the cooling line 10or the fuel cell 2. Here, if a demand for heating is encountered whenthe operation of the fuel cell system 1 is stopped once and thenrestarted in a short time and if the cooling water in the exhaust heatutilization line 11 is allowed to flow into the fuel cell 2 prior to thecooling water in the cooling line 10, then a temperature difference inthe cooling water undesirably causes a thermal shock to the fuel cell 2.According to the present embodiment, therefore, control is carried outsuch that the flow of the cooling water in the exhaust heat utilizationline 11 is begun after the flow of the cooling water in the cooling line10 is begun.

1. At Start-Up

Specifically, if an input of the demand for heating is supplied to theinput means 52 when starting-up (warming-up) the fuel cell 2, thecontroller 3 starts the driving of the cooling pump 23 and then startsthe driving of the exhaust heat utilization pump 42. This causes theflow of the cooling water in the exhaust heat utilization line 11 to bedelayed from the flow of the cooling water of the cooling line 10, thusallowing the cooling water of the cooling line 10 to flow into the fuelcell 2 first. Hence, even if there is a considerable temperaturedifference in cooling water between the cooling line 10 and the exhaustheat utilization line 11, a temperature change in the fuel cell 2 willbe suppressed.

At this time, if the controller 3 starts the driving of the exhaust heatutilization pump 42 after the flow rate of the cooling water by thecooling pump 23 has sufficiently increased, then a temperature change inthe fuel cell 2 can be further suppressed. More specifically, thecontroller 3 preferably carries out flow rate control such that the flowrate of the cooling water by the cooling pump 23 is larger than the flowrate of the cooling water by the exhaust heat utilization pump 42 in aninitial period of the driving, during which both pumps 23 and 42 arecooperatively controlled. Further, the driving of the exhaust heatutilization pump 42 is preferably controlled such that the flow rate ofthe cooling water of the exhaust heat utilization line 11 graduallyincreases.

The timing at which the driving of the exhaust heat utilization pump 42is begun may be a timing at which, for example, a predetermined timestored in the ROM beforehand has elapsed since the driving of thecooling pump 23 was begun or a timing based on a detection result of aflow rate sensor, not shown, provided at, for example, the cooling waterinlet 2 a of the fuel cell 2 in the cooling line 10. Further, in anothermode, the driving of the exhaust heat utilization pump 42 may be begunwhen the number of revolutions of the cooling pump 23 reaches apredetermined number or more, for example, when the cooling pump 23 hascompletely started up. Incidentally, the number of revolutions of thecooling pump 23 may be detected by an RPM sensor connected to thecooling pump 23.

The time from the stop of the fuel cell 2 to the next start-up of thefuel cell 2 may be measured by a timer, which is incorporated in thecontroller 3, in cooperation with or independently from a flow sensor,and based on the length of the measured time, the start time at whichthe driving of the exhaust heat utilization pump 42 is started may bevaried. Thus, if the stop time of the fuel cell 2 is relatively long,the start of the driving of the exhaust heat utilization pump 42 doesnot have to be delayed relative to the start of the driving of thecooling pump 23. Further, if the stop time of the fuel cell 2 isrelatively short, the start of the driving of the exhaust heatutilization pump 42 can be sufficiently delayed until the flow rate ofthe cooling water in the cooling line 10 sufficiently increases.

Further preferably, the start time at which the driving of the exhaustheat utilization pump 42 is started is varied based on the temperaturesensors 61 to 65 in cooperation with or independently from the flowsensor or the timer. For instance, the heat radiation condition of thecooling water at each portion varies depending on the environment inwhich the fuel-cell vehicle is placed, so that the temperature change inthe fuel cell 2 can be further restrained by using the plurality oftemperature sensors 61 to 65, which detect the temperature of thecooling water, rather than by setting the start time of the driving ofthe exhaust heat utilization pump 42 only by the timer.

For example, the start time of the driving of the exhaust heatutilization pump 42 is set based on the temperature difference betweenthe cooling water in the fuel cell 2 and the cooling water in theexhaust heat utilization line 11 from detection results of thetemperature sensor 64 at the cooling water outlet 2 b of the fuel cell 2and the temperature sensor 65 of the exhaust heat utilization line 11,in particular, among the plurality of temperature sensors 61 to 65.Alternatively, the start time of the driving of the exhaust heatutilization pump 42 is set based on the temperature difference in thecooling water between the cooling line 10 and the exhaust heatutilization line 11 from the detection results of the temperature sensor61 and the temperature sensor 65. At this time, if there is notemperature difference, then the driving of the cooling pump 23 and theexhaust heat utilization pump 42 may be simultaneously started. Thus,the driving conditions of the cooling pump 23 and the exhaust heatutilization pump 42 may be changed according to the temperature of thecooling water.

Further, in place of the control configuration described above, thecontroller 3 may simultaneously starts the driving of the cooling pump23 and the exhaust heat utilization pump 42 when an input of the demandfor heating is supplied to the input means 52 when starting-up the fuelcell 2. It is necessary, however, to carry out flow control such thatthe flow rate of the cooling water by the cooling pump 23 is higher thanthe flow rate of the cooling water by the exhaust heat utilization pump42 in order to avoid a temperature change in the cooling water flowinginto the fuel cell 2. Conducting such flow control makes it possible tobring the temperature of the merged cooling water from the cooling line10 and the exhaust heat utilization line 11 close to the temperature ofthe cooling water of the cooling line 10. This type of flow rate controlcan be accomplished by RPM control over the cooling pump 23 and theexhaust heat utilization pump 42 or the duty ratio control.

Further, in place of the control configuration described above, even ifno input of the demand for heating is supplied to the input means 52when starting-up the fuel cell 2, the controller 3 may start, at everystart-up of the fuel cell 2, the driving of the exhaust heat utilizationpump 42 after starting the driving of the cooling pump 23, and performthe driving of the exhaust heat utilization pump 42 for a predeterminedtime. It is needless to say that, at this time, the flow rate controlmay be carried out such that the flow rate by the cooling pump 23becomes larger, while simultaneously starting the driving of the coolingpump 23 and the exhaust heat utilization pump 42.

This control configuration is more advantageous than the configurationin which the cooling water in the exhaust heat utilization line 11 doesnot flow without exception when no input is supplied to the input means52. To be specific, if heating is not used for an extended period oftime during the summer or the like, the cooling water in the exhaustheat utilization line 11 may remain therein, possibly causing a problem,such as foreign matters building up or algae growing in the exhaust heatutilization line 11. According to the aforesaid control configuration,the exhaust heat utilization pump 42 is briefly driven when starting-upthe fuel cell 2 whether there is a demand for heating or not (regardlessof an input to the input means 52), so that the cooling water in theexhaust heat utilization line 11 flows, thus making it possible toproperly obviate the aforesaid problems.

As described above, conducting various types of flow rate control makesit possible to avoid a thermal shock to the fuel cell 2 due to thecooling water of the exhaust heat utilization line 11 when starting-upthe fuel cell 2. If both the cooling pump 23 and the exhaust heatutilization pump 42 are being driven when stopping the fuel cell 2, thenthe driving of the exhaust heat utilization pump 42 is stopped first,and then the driving of the cooling pump 23 is stopped thereafter. Thismakes it possible to stop the flow of the cooling water of the exhaustheat utilization line 11 preferentially over the flow of the coolingwater in the cooling line 10, allowing a temperature change in the fuelcell 2 to be ideally restrained.

2. During Intermittent Operation

A brief explanation will now be given to the flow control of the coolingwater during an intermittent operation of the fuel cell 2. Theintermittent operation of the fuel cell 2 means that the supply ofelectric power from the fuel cell 2 to a load is temporarily stopped,and electric power is supplied from a secondary cell to the load. Theintermittent operation is accomplished by intermittently supplying fuelgas and oxidant gas to the fuel cell 2 and by maintaining the open endvoltage of the fuel cell 2 within a predetermined range. In theintermittent operation, there is a case where the driving of a pump isstopped to stop the flow of the cooling water to be circulated to thefuel cell 2.

In the fuel cell system 1 according to the present embodiment, thecontroller 3 continues the driving of the cooling pump 23 by theelectric power supplied from the secondary cell to continue the flow ofcooling water to the fuel cell 2 during the intermittent operation ofthe fuel cell 2. With this configuration, the temperature of the fuelcell 2 can be properly controlled also during the intermittentoperation.

It is also possible to circulate the cooling water of the exhaust heatutilization line 11 into the fuel cell 2 by driving the exhaust heatutilization pump 42 rather than the cooling pump 23. Preferably,however, when the exhaust heat utilization pump 42 is driven in theintermittent operation, the driving of the exhaust heat utilization pump42 is begun after the driving of the cooling pump 23 is begun. It isneedless to say that, at this time, the flow rate control may beconducted such that the flow rate by the cooling pump 23 becomes larger,while starting the driving of the cooling pump 23 and the exhaust heatutilization pump 42 simultaneously. This is to obviate a thermal shockbeing applied to the fuel cell 2 attributable to the cooling water inthe exhaust heat utilization line 11, as described above, also duringthe intermittent operation.

The following will explain a second embodiment through a seventhembodiment. The control example explained in the first embodiment can beapplied to all these embodiments. To avoid repeated description, thefollowing explanation will give the same reference characteristics tothe same parts as those in the first embodiment and will focus ondifferent aspects from the first embodiment in order to avoid repeateddescription.

SECOND EMBODIMENT

Referring to FIG. 3, a fuel cell system 1 according to a secondembodiment will be explained. The second embodiment is different fromthe first embodiment in that there is only one pump 71 for circulatingcooling water and accordingly pressure drop tuning is carried out on acooling line 10 and an exhaust heat utilization line 11.

The pump 71 in the present embodiment is provided on the upstream sideof a branch point 14 of the cooling line 10 and the exhaust heatutilization line 11. The pump 71, however, may be provided on thedownstream side of the confluence 13. The driving of the pump 71 iscontrolled by a controller 3, and pressure-feeds cooling water in thecooling line 10 and the exhaust heat utilization line 11. In cooperationwith the controller 3, the pump 71 functions as a flow control means forcontrolling the flow of the cooling water in the cooling line 10 and theexhaust heat utilization line 11. As with the first embodiment, the flowcontrol means restrains the inflow of cooling water that has atemperature difference from a fuel cell 2 into the fuel cell 2.

The flow passage resistance of the cooling water in the cooling line 10is set to be lower than the flow passage resistance of the cooling waterin the exhaust heat utilization line 11. As the pressure drop tuning forsetting the flow passage resistance, the diameter of the exhaust heatutilization line 11 is set to about 1/10 of the diameter of the coolingline 10. Alternatively, however, a throttling part, such as an orifice,for making it difficult for the cooling water to flow through may beprovided at some midpoint of the exhaust heat utilization line 11.

According to the present embodiment, even if the pump 71 is driven at astart-up or during an intermittent operation of the fuel cell 2, thepressure drop tuning described above causes the cooling water in thecooling line 10 to start flowing into the fuel cell 2 preferentiallyover the cooling water in the exhaust heat utilization line 11. Withthis configuration, a temperature change at a start-up or the like ofthe fuel cell 2 can be restrained even if the number of the pumps hasbeen reduced by one. Moreover, since the flow of the cooling water iscontrolled by the single pump 71, the control can be simplified.

The exhaust heat utilization line 11 may be provided with a shut valve,and the shut valve may be opened when there is a demand for heating,while the shut valve may be closed if there is no demand for heating.Further, the shut valve may be opened/closed according to a measurementresult of the timer or detection results of the flow sensor or thetemperature sensors 61 to 65 described above. For example, if an inputof the demand for heating is supplied to an input means 52 when the fuelcell 2 is started up, then the timing for opening the shut valve thathas been closed can be set on the basis of detection results of thetimer or various sensors.

Further, as a modification of the second embodiment, the confluence 13or a branch point 14 of the cooling line 10 and the exhaust heatutilization line 11 may be provided with a switching valve 73 forswitching the flow of the cooling water between the cooling line 10 andthe exhaust heat utilization line 11 (FIG. 3 shows only signal linesfrom the controller 3). The switching valve 73, which can be configuredin the same manner as the switching valve 24 adjacent to the radiator 21described above, is connected to the controller 3. The switching valve73, together with the pump 71 and the controller 3, constitutes a flowcontrol means that controls the flow of the cooling water in the coolingline 10 and the exhaust heat utilization line 11.

Further, when beginning the flow of the cooling water in the exhaustheat utilization line 11 into the fuel cell 2, the controller 3 changesthe switching valve 73 over to the cooling line 10 to first start theflow of the cooling water of the cooling line 10 into the fuel cell 2.Thereafter, the switching valve 73 is changed over to both the coolingline 10 and the exhaust heat utilization line 11 so as to allow thecooling water of the cooling line 10 and the exhaust heat utilizationline 11 to flow into the fuel cell 2. Controlling the switching valve 73as described above also makes it possible to start the flow of thecooling water of the cooling line 10 preferentially over the exhaustheat utilization line 11 into the fuel cell 2, so that a temperaturechange in the fuel cell 2 can be restrained. Moreover, the need forcomplicated pressure drop tuning of the cooling line 10 and the exhaustheat utilization line 11 is obviated.

THIRD EMBODIMENT

Referring to FIG. 4, a fuel cell system 1 according to a thirdembodiment will be explained. The third embodiment is different from thefirst embodiment in the positions of a confluence 13 and a branch point14. To be specific, the confluence 13 and the branch point 14 areprovided adjacently to a cooling water outlet 2 b of a fuel cell 2, andthe confluence 13 is provided at the downstream side of the branch point14 and at the upstream side of a cooling pump 23. This piping systemmakes it possible to provide the same advantages as those of the firstembodiment by carrying out cooperative control over the cooling pump 23and an exhaust heat utilization pump 42 in the same manner as the firstembodiment.

Especially in the present embodiment, when starting-up the fuel cell 2,it is preferred to first change a switching valve 24 over to a bypasspassage 22 to start the driving of the cooling pump 23 and then changethe switching valve 24 over to a radiator 21, while starting the drivingof the exhaust heat utilization pump 42. The cooling pump 23 mayalternatively be positioned on the downstream side of the radiator 21,and the exhaust heat utilization pump 42 may alternatively be positionedon the downstream side of a heater core 41.

FOURTH EMBODIMENT

Referring to FIG. 5, a fuel cell system 1 according to a fourthembodiment will be explained. The fourth embodiment is different fromthe first embodiment in that a bypass line 81 for circulating coolingwater, bypassing a fuel cell 2, a shut valve 82 is provided between thedownstream side of a confluence 13 and a cooling water inlet 2 a of thefuel cell 2, and a shut valve 83 is provided between the upstream sideof a branch point 14 and a cooling water outlet 2 b of the fuel cell 2.

The bypass line 81 has one end, which is the upstream end, connected tothe downstream side of the switching valve 24 in a cooling line 10, andthe other end, which is the downstream end, connected to the upstreamside of the cooling pump 23 in the cooling line 10. The bypass line 81is provided with a shut valve 84 for opening/closing the bypass line 81.Each of two shut valves 82 and 83 near the fuel cell 2 is composed of,for example, an electromagnetic valve, and the opening/closingoperations thereof are controlled by a controller 3. The bypass line 81and the three shut valves 82, 83, and 84 are used to obviate a thermalshock to the fuel cell 2 caused by cooling water of an exhaust heatutilization line 11.

For instance, when starting-up the fuel cell 2, if an input of thedemand for heating is supplied or not supplied to an input means 52, thecontroller 3 first closes the two shut valves 82 and 83 near the fuelcell 2 and opens the shut valve 84 of the bypass line 81. Thereafter,the controller 3 begins the driving of both the cooling pump 23 and anexhaust heat utilization pump 42. This causes the cooling water of thecooling line 10 and the cooling water of the exhaust heat utilizationline 11 to merge at the upstream end of the bypass line 81 and to bemixed while flowing through the bypass line 81. Then, the cooling waterof the bypass line 81 is branched at the downstream end of the bypassline 81 and flows back into the cooling line 10 and the exhaust heatutilization line 11, bypassing the fuel cell 2.

With this configuration, even if there is a temperature difference incooling water between the cooling line 10 and the exhaust heatutilization line 11 or if there is a local temperature difference incooling water in the cooling line 10 and the exhaust heat utilizationline 11, the temperature of the cooling water will be leveled. And, tostart the circulation of the cooling water into the fuel cell 2 after apredetermined time elapses from the start of the driving of the coolingpump 23 and the exhaust heat utilization pump 42, the two shut valves 82and 83 near the fuel cell 2 are opened, while the shut valve 84 of thebypass line 81 is closed. Carrying out such control makes it possible torestrain a temperature change in the fuel cell 2 attributable to thecooling water of the exhaust heat utilization line 11.

When controlling the flow when starting-up the fuel cell 2, the time forwhich the cooling water runs in the bypass line 81 or the rotationalamount of the cooling pump 23 or the exhaust heat utilization pump 42may be controlled based on the timer or the detection results of varioussensors, such as the temperature sensors 61 to 65, as with the firstembodiment. Further, the same control as that in the first embodimentmay be conducted to intermittently operate or to stop the fuel cell 2.The bypass line 81, which has been positioned adjacently to the coolingline 10, may be of course provided adjacently to the exhaust heatutilization line 11.

Further, the three shut valves 82 through 84 have been provided;however, the number thereof is not limited thereto. For example, one ofthe two shut valves 82 and 83 near the fuel cell 2 can be omitted. Thebypass line 81 has been provided with the shut valve 84, however, inplace of the shut valve, a switching valve, for example, that has thesame structure as that of the aforesaid switching valve 24 may beprovided at the junction of the bypass line 81 and the cooling line 10.

FIFTH EMBODIMENT

Referring now to FIG. 6, a fuel cell system 1 according to a fifthembodiment will be explained. The present embodiment has a check valve91 added to the fuel cell system 1 according to the third embodimentshown in FIG. 4. The check valve 91 is installed on a cooling line 10between a confluence 13 and a branch point 14. The check valve 91 blocksthe flow of cooling water from the confluence 13 to the branch point 14.

The operation of the present embodiment will be described. If an exhaustheat utilization pump 42 is driven when a cooling pump 23 is not beingdriven, then the cooling water that has passed through an exhaust heatutilization line 11 may partly flow from the confluence 13 to the branchpoint 14. The present embodiment is provided with the check valve 91,making it possible to block the flow of the cooling water from theconfluence 13 to the branch point 4 and to block the inflow of thecooling water into a cooling water outlet 2 b of a fuel cell 2. Withthis configuration, the fuel cell 2 is not subjected to a thermal shockeven if the temperature of the cooling water of the exhaust heatutilization line 10 is lower than the temperature of the fuel cell 2.

The present embodiment is also capable of providing the same advantagesas those of the aforesaid embodiment by carrying out the cooperativecontrol of the cooling pump 23 and the exhaust heat utilization pump 42,as described in the third embodiment and the first embodiment. Further,the check valve 91 may alternatively be provided between the branchpoint 14 and the cooling water outlet 2 b of the fuel cell 2.

SIXTH EMBODIMENT

Referring now to FIG. 7, a fuel cell system 1 according to a sixthembodiment will be explained. The present embodiment shares the samepiping system with the fuel cell system 1 according to the thirdembodiment shown in FIG. 4, but differs in control system. To bespecific, the third embodiment has the single controller 3 as oneexample of a control system, while the present embodiment has twocontrollers 3 and 3′. The two controllers 3 and 3′ correspond to a partof “flow control means” or “control means” described in the claims.

One controller 3 (ECU) controls the driving of a cooling pump 23, an RPMsensor 92 of the cooling pump 23 being connected thereto. Further, thecontroller 3 functions as a main controller that controls also aswitching valve 24, various sensors, such as temperature sensors 61through 65, being connected thereto. The other controller (ECU) 3′controls the driving of an exhaust heat utilization pump 42. A controlcircuit located between the controller 3′ and the exhaust heatutilization pump 42 is provided with two relays 93 and 94. Thecontroller 3′ opens/closes the relay 93, while the controller 3opens/closes the relay 94.

The control system of the present embodiment also makes it possible toprovide the same operations and advantages as those of the aforesaidembodiments. For instance, when starting-up the fuel cell 2, if the RPMsensor 92 detects that the RPM of the cooling pump 23 has reached apredetermined number or more, then the controller 3 may close the relay94 and enable the driving of the exhaust heat utilization pump 42. And,the controller 3′ may close the relay 93 and control the driving of theexhaust heat utilization pump 42. This makes it possible to restrain thecooling water of the exhaust heat utilization line 11 from flowingbackward to a cooling water outlet 2 b of the fuel cell 2, and torestrain a temperature change in the fuel cell 2.

SEVENTH EMBODIMENT

Referring now to FIG. 8, a fuel cell system 1 according to a seventhembodiment will be explained. The seventh embodiment differs from thesixth embodiment in that a controller 3 communicates with a controller3′. For instance, at a start-up of a fuel cell 2, the controller 3notifies the controller 3′ of a permission to drive an exhaust heatutilization pump 42, and in response thereto, the controller 3′ closes arelay 93 and controls the driving of the exhaust heat utilization pump42. Thus, the same operations and advantages as those of the sixthembodiment can be provided. An advantage over the sixth embodiment isthat the relay (94) is no longer necessary, thus permitting reduced costto be achieved.

In each of the aforesaid embodiments, the heat energy of exhaust heat ofthe fuel cell 2 has been used for heating; however, if the fuel cellsystem 1 is, for example, a fixed type, then the heat energy of theexhaust heat of the fuel cell 2 can be used for hot-water supply orbath. In such a case, a heat exchanger for heating (a heater core 41) ofthe exhaust heat utilization line 11 heat-exchanges with a medium otherthan an air conditioning gas. Controlling the flow of cooling water inthe same manner as described above is effective for the fuel cell 2.

EIGHTH EMBODIMENT

FIG. 9 is a system diagram showing a cooling apparatus for a fuel cell,which is a part of a fuel cell system 1. A fuel cell 100 to which fuelgas and oxidant gas are supplied has a stack structure composed of alaminate of multiple unit cells, which are basic units. The fuel cell100 is housed, together with a peripheral detecting device and the like,in a stack case 200. The stack case 200 is formed of a metal or hardresin material and fixed to the bottom of the floor or the like of avehicle interior through the intermediary of a bracket or the like.

The fuel cell 100 comes in a plurality of types, including aphosphoric-acid type; the fuel cell in the present embodiment iscomposed of a solid polymer electrolytic type, which is ideally suitedfor installation in a vehicle. Although not shown, a unit cell of thefuel cell 100 is formed by an MEA (Membrane Electrode Assembly)sandwiched between a pair of separators made of a metal or the like. Asinner flow passages of the stack-structured fuel cell 100, a flowpassage of fuel gas, a flow passage of oxidant gas, and a flow passageof cooling water are provided. These flow passages are formed primarilyin the planes of the separators. The fuel cell 100 is cooled by thecooling water serving as a refrigerant flowing through the inner flowpassages by a cooling apparatus 101.

The cooling apparatus 101 includes a radiator 110 which cools coolingwater discharged from a fuel cell 100, a circulation passage 120 throughwhich the cooling water is circulated between the radiator 110 and thefuel cell 100, a bypass passage 130 for bypassing the radiator 110, apump 140 which is positioned on the circulation passage 120 at thedownstream side of the fuel cell 100 and which pressure-feeds coolingwater, a fluidic valve 150 which sets the flow of cooling water to theradiator 110 and the bypass passage 130, and a controller 160 whichoverall controls the entire cooling apparatus 101. The circulationpassage 120 and the bypass passage 130 function as a refrigerantcirculation system which circulatively supplies a refrigerant to thefuel cell.

The radiator 110 (a heat exchanger) has therein a passage that leads thecooling water whose temperature has risen due to an electric generationreaction of the fuel cell 100, and the heat of the cooling water isdissipated outside when the cooling water passes through the passage.The radiator 110 is provided, for example, on the front of a vehicle.The radiator 110 is also provided with a fan 180 for blowing outside airto the passage in the radiator 110. The fan 180 accelerates the coolingof the cooling water in the radiator 110. The fan 180 is connected tothe controller 160 and the drive thereof is controlled by the controller160.

The circulation passage 120 is composed primarily of a first passage 210from a cooling water outlet 100 b of the fuel cell 100 to an inlet ofthe radiator 110, a second passage 220 from an outlet of the radiator110 to a first port 150 a of the fluidic valve 150, and a third passage230 from a second port 150 b of the fluidic valve 150 to a cooling waterinlet 100 a of the fuel cell 100.

The upstream end of the bypass passage 130 is connected to thedownstream end of the pump 140 of the first passage 210, while thedownstream end thereof is connected to a third port 150 c of the fluidicvalve 150. The bypass passage 130 is composed of a tube having an insidediameter that is smaller than or equal to that of the circulationpassage 120. The bypass passage 130 is provided with no auxiliary devicehaving a cooling effect. The cooling water flows into the bypass passage130 from the first passage 210 of the circulation passage 120, bypassingthe radiator 110. Subsequently, the cooling water that has passedthrough the bypass passage 130 passes through the third passage 230 viathe fluidic valve 150 and then flows into the fuel cell 100.

The circulation passage 120 and the bypass passage 130 are provided witha plurality of temperature sensors 310, 320, 330, and 340 along thesepassages in a scattered manner. To be specific, the bypass passage 130is provided with the single temperature sensor 310 near the fluidicvalve 150. The plurality of temperature sensors 320, 330, and 340 on thecirculation passage 120 are provided at a cooling water inlet 100 a ofthe fuel cell 100, a cooling water outlet 100 b thereof, and at thedownstream side of the radiator 110. The temperature sensors 320 and 330near the cooling water inlet 100 a and the cooling water outlet 100 b ofthe fuel cell 100 are housed in a stack case 200. However, thesetemperature sensors 320 and 330 may be provided outside the stack case200.

The temperature sensor 330 (a first temperature sensor) at the coolingwater outlet 100 b detects a temperature that reflects the temperatureof the cooling water in the fuel cell 100. Further, the temperaturesensor 340 (a second temperature sensor) on the downstream side of theradiator 110 detects a temperature that reflects the temperature of thecooling water at the outlet of the radiator 110. These pluraltemperature sensors 310 to 340 are connected to the controller 160, andsupply their detection results to the controller 160.

The pump 140 is connected to the controller 160 and the driving thereofis controlled by the controller 160. When the driving of the pump 40 isbegun, the cooling water in the circulation passage 120 flows andcirculates to the radiator 110 and/or the bypass passage 130. Thus,temperature control is carried out such that the temperature of the fuelcell 100 is maintained within a predetermined range, and the electricgeneration reaction of the fuel cell 100 efficiently proceeds. When thedriving of the pump 140 is stopped, the flow of the cooling water in thecirculation passage 120 stops. The pump 140 has been positioned at theupstream side of the radiator 110 and the fluidic valve 150; it isobvious, however, the pump 140 may alternatively be positioned at thedownstream side of the radiator 110 and the fluidic valve 150.

The fluidic valve 150 has a three-way valve structure having the firstport 150 a, the second port 150 b, and the third port 150 c. The fluidicvalve 150 is configured to allow the cooling water to be switched to oneof the radiator 110 and the bypass passage 130 or to both of them. Forinstance, if the fluidic valve 150 is completely changed over to thebypass passage 130, then the cooling water not subjected to the heatdissipation effect by the radiator 110 will flow into the fuel cell 100.

Further, the fluidic valve 150 is configured such that the openingdegree of the valve can be adjusted, thus making it possible to adjustthe inflow amount of the cooling water into the radiator 110 and thebypass passage 130. For example, as the opening degrees of the fluidicvalve 150, the opening degree for the radiator 110 may be set to 10%,while the opening degree for the bypass passage 130 may be set to 90%.Thus, the fluidic valve 150 functions as a switching means for switchingthe flow of the cooling water between the radiator 110 and the bypasspassage 130, and also makes it possible to vary the opening degree forthe flow.

Hereinafter, the following abbreviations, such as “radi fully opened(the radiation fully opened)” and “bypass fully opened,” will befrequently used in the explanation. The “radi fully opened” means thatthe fluidic valve 150 is fully opened to the radiator 110 while it isfully closed from the bypass passage 130. In the “radi fully opened”condition, the cooling water that has passed through the radiator 110 issupplied to the fuel cell 100, while the supply of the cooling water inthe bypass passage 130 to the fuel cell 100 is shut off. Similarly, “thebypass fully opened” means that the fluidic valve 150 is fully opened tothe bypass passage 130, while it is fully closed from the radiator 110.In “the bypass fully opened” condition, the cooling water that haspassed through the bypass passage 130 is supplied to the fuel cell 100,while the supply of the cooling water that has passed through theradiator 110 is shut off.

The fluidic valve 150 is connected to the controller 160, and theopening degree of the valve, including a switching operation, iscontrolled by output signals from the controller 160. This type offluidic valve 150 may be composed of, for example, an electromagneticvalve type driven by a solenoid, a motor-operated valve type driven by amotor, or a type driven by electric/magnetic forces of a piezoelectricelement or a magnetostrictive element. Incidentally, the fluidic valve150 is ideally formed of a rotary valve, as will be discussed later inother embodiments.

Reference numeral 410 in the figure denotes a position sensor built inthe fluidic valve 150. The position sensor 410 detects the position ofthe valving-element of the fluidic valve 150, i.e., the opening degreeof the valve. A detection result of the position sensor 410 is input tothe controller 160.

Generally, a drift or the like of the position sensor 410 may lead todeteriorated accuracy thereof, so that the fluidic valve 150 issubjected to zero point adjustment to reset the position sensor 410. Thezero point adjustment is usually performed at a start-up of the fuelcell 100 (at a start-up of the fuel cell system 1). Carrying out thezero point adjustment eliminates, from the fluidic valve 150, thedifference between an opening degree based on a command value of thecontroller 160 and an actual opening degree set on the basis of thecommand before the fuel cell 100 is actually actuated. This allows theopening degree of the fluidic valve 150 to be controlled with highaccuracy when the fuel cell 100 generates electric power.

The controller 160 (ECU) has mainly a CPU, a ROM storing controlprograms and control data to be processed by the CPU, and a RAM used asvarious work areas primarily for control processing, none of which areshown. The controller 160 receives detection signals from varioussensors, including the plurality of temperature sensors 310 to 340 andthe position sensor 410. Further, the controller 160 outputs controlsignals to various drivers to control the pump 140, the fluidic valve150, etc., thereby integrally controlling the entire cooling apparatus101. From another viewpoint, the controller 160 functions, incooperation with the pump 140 and the fluidic valve 150, as a flowcontrol means for restraining the cooling water that has a predeterminedtemperature difference from that of the fuel cell 2 from flowing intothe fuel cell 2.

FIG. 10 is a flowchart which shows the processing flow of the coolingapparatus 101 when the fuel cell 100 is started up. When starting-up thefuel cell 100, first, the zero point adjustment of the fluidic valve 150is performed (S1). The zero point adjustment is performed by moving thevalving-element of the fluidic valve 150 by the controller 160 to drivea driving source, such as a motor, of the fluidic valve 150 for apredetermined time until the movement of the valving-element isrestricted by a movement end position. The fluidic valve 150 in thepresent embodiment is a switching valve, so that the fluidic valve 150is controlled by the controller 160 until the fluidic valve 150 is fullyswitched to one of the radiator 110 and the bypass passage 130.

For example, the zero point adjustment is implemented until “the radifully opened” is maintained as a state of the fluidic valve 150 for apredetermined time (S2; No). Performing the zero point adjustment at theradi fully opened side makes it possible to supply the cooling waterwhose temperature has been lowered by the radiator 110 to the fuel cell100 when the fuel cell 100 generates electric power even if the fluidicvalve 150 fails by being stuck during the zero point adjustment. Thisprevents the fuel cell 100 from overheating, thus achieving fail-safe.

Alternatively, the zero point adjustment may be performed with “thebypass fully opened” rather than “the radi fully opened.” In this casealso, the zero point adjustment is performed until the bypass fullyopened is maintained as a state of the fluidic valve 150 for apredetermined time (S2; No). This allows the opening degree of thefluidic valve 150 to be promptly set when the bypass fully opened isrequired as the opening degree of the fluidic valve 150 or when anopening degree that is close to the bypass fully open is required afterthe zero point adjustment. Actually, as will be discussed later, ifthere is a large temperature difference in cooling water between theradiator 110 and the fuel cell 100, then the fluidic valve 150 is set tothe bypass fully opened; it is therefore useful to perform the zeropoint adjustment with the bypass fully opened.

After completion of the zero point adjustment (S2; Yes), the control ofthe fluidic valve 150 is begun (S3). The control of the fluidic valve150 is carried out by changing the opening degree of the fluidic valve150 to a predetermined opening degree from the opening degree after thezero point adjustment (the radi fully opened or the bypass fully opened)according to a command of the controller 160. If, however, the zeropoint adjustment is not performed, then the fluidic valve 150 is changedfrom an initial opening degree before the fuel cell 100 is started to apredetermined opening degree.

More specifically, “the initial opening degree” in the present documentrefers to an opening degree of the fluidic valve 150 immediately beforeexecuting the processing flow for starting up the fuel cell 100, and insteps S3 to S4, the opening degree of the fluidic valve 150 is changedfrom the initial opening degree to a predetermined opening degree viathe opening degree obtained after the zero point adjustment. A specificexample of “the initial opening degree” will be described later in aninth embodiment.

Further, “the predetermined opening degree” refers to an opening degreesuited to specifications that does not cause a sudden temperature changein the fuel cell 100 due to the cooling water that starts to flow intothe fuel cell 100 in a subsequent step. The “predetermined openingdegree” may be an opening degree stored beforehand in the ROM of thecontroller 160 or an opening degree set based on a soak time of the fuelcell system 1 (time for which the fuel cell 100 is let stand at a stop).Regarding the latter, for example, the time from a stop of the fuel cell100 to the next start-up is measured by a timer incorporated in thecontroller 160, and the predetermined opening degree is set based on thelength of the soak time.

More in detail, if the soak time is relatively long, then time that isadequate for the cooling water to dissipate heat elapses. For thisreason, the temperatures of the cooling water in the radiator 110 andthe cooling water in the fuel cell 100 become equal. In this case, theopening degree of the fluidic valve 150 when starting-up the fuel cell100 is not a problem, in particular, in relation to a temperature changein the fuel cell 100. Hence, the predetermined opening degree of thefluidic valve 150 can be arbitrarily set. Preferably, the predeterminedopening degree of the fluidic valve 150 is set to the bypass passage 130side, such as “the bypass fully opened,” thus allowing the warm-up timeof the fuel cell 100 to be shortened.

Meanwhile, if the soak time is relatively short, a difference occurs inthe radiation amount of cooling water between the fuel cell 100 insidethe stack case 200 and the radiator 110 outside the stack case 200, andthe temperature of the cooling water in the radiator 110 will be lowerthan that of the fuel cell 100. In this case, therefore, setting thepredetermined opening degree of the fluidic valve 150 to the bypasspassage 130 side, such as “the bypass fully opened,” makes it possibleto prevent the cooling water in the radiator 110 from flowing into thefuel cell 100. Thus, a temperature change in the fuel cell 100 can besuppressed.

And preferably, in cooperation with or independently of a timer, thepredetermined opening degree of the fluidic valve 150 is set based onthe temperature sensors 310, 320, 330, and 340. For example, the heatradiation condition of the cooling water at each portion variesdepending on the environment in which a fuel-cell vehicle is placed, sothat the fluidic valve 150 is set to the predetermined opening degree onthe basis of the detection results of the plurality of temperaturesensors 310, 320, 330, and 340 that detect the temperature of coolingwater rather than uniquely setting the fluidic valve 150 to thepredetermined opening degree by a timer. This makes it possible tofurther suppress a temperature change in the fuel cell 100.

To be specific, the fluidic valve 150 is set to a predetermined openingdegree based on a temperature difference between the cooling water inthe fuel cell 100 and the cooling water in the radiator 110 according tothe detection results of the temperature sensor 330 and the temperaturesensor 340, in particular, of the fuel cell 100 among the plurality oftemperature sensors 310 to 340. For instance, if the temperaturedifference exceeds a first predetermined threshold value, then “thebypass fully opened” is set as the predetermined opening degree. If thetemperature difference is not more than a second predetermined thresholdvalue, which is lower than the first predetermined threshold value, thenany opening degree, such as “the radi fully opened,” may be set as thepredetermined opening degree.

However, the cooling water may circulate through both the bypass passage130 and the radiator 110 whether a temperature difference is the firstpredetermined threshold value or more or the second predeterminedthreshold value or less. In this case, the circulation ratio (flow rateratio) may be set, as necessary. Further, the fluidic valve 150 may beset to a predetermined opening degree based on one temperature sensor(one of 310 to 340) in addition to a temperature difference of detectionresults.

After the fluidic valve 150 is changed to the predetermined openingdegree (S4; Yes), the driving of the pump 140 is begun based on thecommand of the controller 160 (S5). The timing at which the driving ofthe pump 140 is begun may be immediately after or at the same time thefluidic valve 150 is changed to a predetermined opening degree. In otherwords, the processing for changing the opening degree of the fluidicvalve 150 is required to be completed before the processing for startingthe driving of the pump 140 is executed. When the driving of the pump140 is begun, the cooling water is supplied to the fuel cell 100 throughthe intermediary of the fluidic valve 150 set to the predeterminedopening degree and the operation (the generation of electric power) ofthe fuel cell 100 is begun (S6).

As described above, according to the cooling apparatus 101 provided inthe fuel cell system 1, when starting-up the fuel cell 100, the fluidicvalve 150 is set to the predetermined opening degree preferentially overthe start of the driving of the pump 140. Thus, a temperature change inthe fuel cell 100 can be ideally restrained. This makes it possible toobviate thermal influences, such as the distortion of the separatorscaused by thermal shocks, when starting-up the fuel cell 100, permittinghigher reliability of the fuel cell 100 to be achieved. Moreover, sincethe zero point adjustment of the fluidic valve 150 is performed, theopening degree of the fluidic valve 150 can be controlled, as necessary,to the bypass passage 130 or the radiator 110 with high accuracy whilethe fuel cell 100 is generating electric power.

In the present embodiment, the zero point adjustment of the fluidicvalve 150 has been carried out; however, if the fluidic valve 150 is ahigh-accuracy valve, then it is unnecessary to perform the zero pointadjustment.

Further, the fluidic valve 150 has been provided at the downstream sideof the radiator 110; alternatively, however, the fluidic valve 150 maybe provided at the upstream side of the radiator 110.

NINTH EMBODIMENT

A cooling apparatus 101 in a fuel cell system 1 according to a ninthembodiment will be explained. FIG. 11 is a flowchart which shows theprocessing flow of the cooling apparatus 101 when a fuel cell 100 isstopped. As shown in the figure, when the operation of the fuel cell 100is stopped (S11), first, the driving of a pump 140 is stopped by acontroller 160 (S12). Subsequently, the control of a fluidic valve 150is begun (S13). The control of the fluidic valve 150 is implemented bychanging the opening degree of the fluidic valve 150 from the openingdegree before the stop to the aforesaid “initial opening degree” by thecommand of the controller 160.

Here, if the fluidic valve 150 is set to an opening degree whichincludes “the radi fully opened” that allows cooling water to flow intothe radiator 110, as an initial opening degree, then the natural heatdissipation of the cooling water in the fuel cell 100 can be acceleratedat a stop of the fuel cell 100. Moreover, the aforesaid zero pointadjustment on “the radi fully opened” side can be promptly performed.Alternatively, the initial opening degree may be set to an openingdegree, which includes “the bypass fully opened,” at which the fluidicvalve 150 allows cooling water to flow into a bypass passage 130. Thismakes it possible to promptly perform the zero point adjustment on “thebypass fully opened” side.

Further, as an alternative of the aforesaid opening degrees, the initialopening degree may be set to an opening degree at which the fluidicvalve 150 allows a refrigerant to circulate into both the radiator 110and the bypass passage 130. The ratio of both in this case may be set,as appropriate. Setting to this opening degree makes it possible torestrain the fuel cell 100 engaged in an electricity generatingoperation from overcooling and overheating if the fluidic valve 150fails, thus permitting fail-safe to be ideally achieved. Moreover, thezero point adjustment can be promptly performed to both “the radi fullyopened” and “the bypass fully opened.” When the initial opening degreeof the fluidic valve 150 is set, the processing flow is finished (S14;Yes).

Then, when the fuel cell 100 is restarted in a predetermined stop timeof the fuel cell 100, the cooling apparatus 101 is driven according tothe flow shown in FIG. 10. More specifically, when an attention isfocused on the fluidic valve 150, the opening degree of the fluidicvalve 150 is changed from “the initial opening degree” set at a stop ofthe fuel cell 100 to a zero-point-adjustment opening degree and then to“a predetermined opening degree” thereafter.

TENTH EMBODIMENT

Referring now to FIGS. 12 and 13, a configuration example of a fluidicvalve 150 will be explained as a tenth embodiment of a cooling apparatus101 in a fuel cell system 1 in accordance with the present invention.The fluidic valve 150 in the present embodiment is constituted of arotary valve 500 whose valve opening degree is adjustable in anelectrical control manner. The fluidic valve 150 constituted of therotary valve 500 makes it possible to properly and accurately deal witha fuel cell 100, which is sensitive to temperature control.

FIG. 12 shows an essential part of the internal structure of the rotaryvalve 500. A valving-element 510 in the rotary valve 500 is positionedat a confluence of a second passage 220 from a radiator 110, a bypasspassage 130, and a third passage 230 in communication with the fuel cell100. The rotary valve 500 has a stepping motor 520 serving as a drivingsource for rotating the valving-element 510, a train of gears 530 and540, which transmits a motive power from the stepping motor 520 to thevalving-element 510, and a position restricting mechanism 550 thatrestricts an end position of the rotation of the valving-element 510.

The valving-element 510 has an opening 570 in the circumferentialdirection, which provides variable communication between the secondpassage 220 and the third passage 230 or between the bypass passage 130and the third passage 230. The upper central portion of thevalving-element 510 is coaxially connected, through the intermediary ofa rod 580, to the central portion of the bottom surface of the finalgear 540 of the train of gears 530 and 540. The position of the opening570 changes as the valving-element 510 rotates, and the rotary valve 500is set at an opening degree based on the position of the opening 570 atwhich the rotation of the valving-element 510 stops.

FIG. 13(A) shows a state of the rotary valve 500 at “the bypass fullyopened.” In this state, the opening 570 of the valving-element 510 facesthe bypass passage 130, causing the bypass passage 130 to be incommunication with the third passage 230. FIG. 13(B) illustrates thestate of the rotary valve 500 at “the radi fully opened.” In this state,the opening 570 of the valving-element 510 faces the second passage 220adjacent to the radiator 110, causing the second passage 220 and thethird passage 230 to be in communication. FIG. 13(C) illustrates thestate in which one half of the opening 570 of the valving-element 510faces the bypass passage 130, while the remaining half of the opening570 faces the second passage 220. In this state, both the bypass passage130 and the second passage 220 are in communication with the thirdpassage 230.

The stepping motor 520 is connected to the controller 160 and configuredsuch that it may be driven and rotated in normal and reverse directions.For instance, if the stepping motor 520 is driven and rotated in thenormal direction, then the valving-element 510 is rotated in the normaldirection and the opening degree of the rotary valve 500 is shiftedtoward “the bypass fully opened.” Meanwhile, if the stepping motor 520is driven and rotated in the reverse direction, then the valving-element510 is rotated in the negative direction and the opening degree of therotary valve 500 is shifted toward “the radi fully opened.” Controllingthe number of steps of the stepping motor 520 allows the opening 570 ofthe valving-element 510 to be moved to a desired position (openingdegree).

The position restricting mechanism 550 has a base 710, two stoppers 720and 730 vertically provided on the base 710, and two restricting slots740 and 750 formed by cutting through the final gear 540. The base 710has a through hole for inserting the rod 580 therein. The tworestricting slots 740 and 750 are provided such that they oppose eachother, sandwiching the center of the final gear 540 therebetween, andthey are formed by arc-shaped slots having the aforesaid center as theircenter of curvature. The stoppers 720 and 730 are inserted in the tworestricting slots 740 and 750, respectively, and the stoppers 720 and730 are configured so that they may slide within the restricting slots740 and 750. Abutting of the stoppers 720 and 730 against the inner endsof the restricting slots 740 and 750 restricts the end position of therotation of the valving-element 510. The position restricting mechanism550 functions when performing the zero point adjustment of the rotaryvalve 500.

To be specific, to implement the zero point adjustment on “the bypassfully opened” side, the stepping motor 520 is driven and rotated in thenormal direction to cause the stopper 720 inserted in the restrictingslot 740 to abut against an end of the restricting slot 740. This ismaintained for a predetermined time to complete the zero pointadjustment (refer to S2 of FIG. 10). Similarly, to perform the zeropoint adjustment on “the radi fully opened,” the stepping motor 520 isdriven and rotated in the reverse direction, and the stopper 730inserted in the other restricting slot 750 is abutted against an end ofthe restricting slot 750. By maintaining this for a predetermined time,the zero point adjustment is completed (again, refer to S2 in FIG. 10).

Incidentally, although a position sensor (the position sensor 410 in theeighth embodiment) that is reset in the zero point adjustment has notbeen shown, the position sensor may be composed of, for example, anoptical rotary encoder. In this case, a rotary plate with slits of therotary encoder may be provided coaxially with the final gear 540,optical paths of a light receiving element and a light emitting elementmay be provided, facing the slits of the rotary plate, and these twoelements may be connected to the controller 160.

ELEVENTH EMBODIMENT

Referring now to FIG. 14, a cooling apparatus 101 in a fuel cell system1 according to an eleventh embodiment will be explained. FIG. 14 showsan example of a time chart of the cooling apparatus 101 at a start-up ofa fuel cell 100.

“Key operation” shown in FIG. 14 refers to an operation of operationmeans for starting up the fuel cell system 1, and refers to, forexample, a key operation for driving a fuel-cell vehicle. “Valve openingdegree” means the opening degree of the fluidic valve 150.

In the present embodiment, the opening degree (initial opening degree)of the fluidic valve 150 at a stop of the fuel cell 100 is set to “theradi fully opened.” When the key operation is performed to start up thefuel cell system 1, the fluidic valve 150 is controlled in responsethereto by making the zero point adjustment of the fluidic valve 150 onthe “bypass fully opened” side. If the fluidic valve 150 is the rotaryvalve 500 in the tenth embodiment, then the zero point adjustment isperformed by abutting the stopper 720 (or 730).

After system check for the fuel cell system 1, such as checking whetherthe zero point adjustment has been completed, the generation of electricpower of a fuel cell 100 is begun, and in synchronization therewith, thedriving of the pump 140 is begun. In other words, according to thepresent embodiment, the aforesaid “predetermined opening degree” of thefluidic valve 150 is the bypass fully opened. This configuration makesit possible to provide the advantages explained in the aforesaidembodiments (the eighth to the tenth embodiments), including thecapability of ideally restraining a temperature change in the fuel cell100 when starting up the fuel cell 100.

TWELFTH EMBODIMENT

FIG. 15 shows a twelfth embodiment of a cooling apparatus 101 in a fuelcell system 1. The twelfth embodiment is a modification example of theeleventh embodiment. A different aspect from the eleventh embodiment isthat the timing at which the driving of the pump 140 is begun isslightly delayed from that in the eleventh embodiment. Morespecifically, the driving of the pump 140 is begun in a predeterminedtime after the zero point adjustment of the fluidic valve 150 iscompleted and the generation of electric power by the fuel cell 100 isbegun. The present embodiment is useful in a case where the zero pointadjustment takes a relatively long time.

THIRTEENTH EMBODIMENT

FIG. 16 shows a thirteenth embodiment of a cooling apparatus 101 in afuel cell system 1. The thirteenth embodiment is a modification exampleof the eleventh embodiment. A different aspect from the eleventhembodiment is the timing at which the driving of a pump 140 is begun.

To be specific, the driving of the pump 140 is begun in the middle ofzero point adjustment for setting the fluidic valve 150 from “the radifully opened,” which is an initial opening degree, to “the bypass fullyopened.” The driving of the pump 140 is begun at the timing when thefluidic valve 150 shuts off the flow of cooling water to the radiator110. If the fluidic valve 150 is, for example, the rotary valve 500 inthe tenth embodiment, then the timing is the instant when the opening570 of the valving-element 510 reaches a position off the second passage220 adjacent to the radiator 110.

The timing at which the driving of the pump 140 is begun is before theopening degree of the fluidic valve 150 reaches “the bypass fullyopened,” and this opening degree allows the cooling water to flow intothe bypass passage 130. Then, after the driving of the pump 140 isstarted, the opening degree of the fluidic valve 150 reaches “the bypassfully opened” and the zero point adjustment is implemented and also thegeneration of electric power by a fuel cell 100 is started.

FOURTEENTH EMBODIMENT

FIG. 17 shows a fourteenth embodiment of a cooling apparatus 101 in afuel cell system 1, the fourteenth embodiment being a modificationexample of the eleventh embodiment. A different aspect from the eleventhembodiment is “the initial opening degree” of the fluidic valve 150,which is set to an opening degree at which the fluidic valve 150 allowscooling water to flow into both the radiator 110 and the bypass passage130. For instance, when this example is applied to the rotary valve 500of the tenth embodiment, the opening degree of the rotary valve 500 isas shown in FIG. 13 (c). This makes it possible to promptly accomplishthe zero point adjustment to “the bypass fully opened,” as describedabove.

Regarding the “initial opening degree” in the present embodiment, theopening degree of the fluidic valve 150 can be changed by design, asappropriate so as to, for example, give priority to either one of theradiator 110 and the bypass passage 130 into which the cooling water isto flow.

FIFTEENTH EMBODIMENT

FIG. 18 shows a fifteenth embodiment of a cooling apparatus 101 in afuel cell system 1, the fifteenth embodiment being a modificationexample of the eleventh embodiment. A different aspect from the eleventhembodiment is “the initial opening degree” of the fluidic valve 150. Tobe specific, “the initial opening degree” is set to an opening degreebefore reaching “the bypass fully opened,” and at this opening degree,the fluidic valve 150 shuts off the flow of cooling water to theradiator 110, while allowing the flow of the cooling water into thebypass passage 130 at the same time. This permits quicker zero pointadjustment to “the bypass fully opened” than in the fourteenthembodiment.

SIXTEENTH EMBODIMENT

Referring now to FIG. 19, a cooling apparatus 101 in a fuel cell system1 according to a sixteenth embodiment will be explained. The sixteenthembodiment is different from the eighth embodiment in that the positionof the pump 140 has been changed onto a third passage 230 on thedownstream side of a fluidic valve 150 and a second radiator 910 isprovided as a sub radiator.

The second radiator 910 has the same construction as the aforesaidradiator 110 (hereinafter referred to as the first radiator), and has afan 920 connected to a controller 160. The upstream end of a secondcirculation passage 940 provided with the second radiator 910 isbranched and connected to a first passage 210, the connected positionbeing at the upstream side of a bypass passage 130. The downstream endof the circulation passage 940 is branched and connected to a secondpassage 220 on the downstream side of the first radiator 110.

This configuration also causes cooling water to be supplied to a fuelcell 100, bypassing the first radiator 110 and the second radiator 910,when the fluidic valve 150 is switched to, for example, the bypasspassage 130 side, such as “the bypass fully opened,” so as to shut offthe flow of the cooling water to the first radiator 110. Meanwhile, ifthe fluidic valve 150 is switched to, for example, the first radiator110 side, such as “the radi fully opened,” then the cooling water thathas been cooled by the first radiator 110 and the cooling water that hasbeen cooled by the second radiator 910 are passed through the fluidicvalve 150 and supplied to the fuel cell 100.

The cooling apparatus 101 in the fuel cell system 1 according to thepresent embodiment also makes it possible to ideally restrain atemperature change in the fuel cell 100 when the fuel cell 100 isstarted up. Moreover, while the fuel cell 100 is generating electricpower, the fuel cell 100 can be cooled further properly by the tworadiators 110 and 910.

1. A fuel cell system comprising: a refrigerant circulating system forcirculating a refrigerant from a fuel cell to the fuel cell, therefrigerant circulating system having flow control means for restrainingthe refrigerant that has a predetermined temperature difference from thefuel cell from flowing into the fuel cell which is generating electricpower.
 2. A fuel cell system which circulates a refrigerant flowing intoa fuel cell to cool the fuel cell and which is capable of heatingair-conditioning gas in an air-conditioning line by exhaust heat of therefrigerant that has passed through the fuel cell, the fuel cell systemcomprising: a cooling line which has a first heat exchanger for coolingthe refrigerant and circulates the refrigerant to the fuel cell; anexhaust heat utilization line which has a second heat exchanger forheat-exchanging the refrigerant with the air-conditioning gas in theair-conditioning line and which circulates the refrigerant to the fuelcell; and flow control means for controlling the flow of the refrigerantin the cooling line and the exhaust heat utilization line, wherein theflow control means starts the flow of the refrigerant in the coolingline, and then starts the flow of the refrigerant in the exhaust heatutilization line.
 3. The fuel cell system according to claim 2, furthercomprising: input means that enables a user to input an instruction forblowing air-conditioning gas of the air-conditioning line, wherein theflow control means controls the flow of the refrigerant in the coolingline and the exhaust heat utilization line based on the input means. 4.The fuel cell system according to claim 3, wherein the flow controlmeans starts the flow of the refrigerant in the cooling line before theflow of the refrigerant in the exhaust heat utilization line if an inputis supplied to the input means, while the flow control means shuts offthe flow of the refrigerant in the exhaust heat utilization line andallows the refrigerant in the cooling line to flow if no input issupplied to the input means.
 5. The fuel cell system according to claim4, wherein the flow control means starts the flow of the refrigerant inthe exhaust heat utilization line after starting the flow of therefrigerant in the cooling line and allows the refrigerant to flow for apredetermined time in the exhaust heat utilization line at a start-up ofthe fuel cell even if no input is supplied to the input means.
 6. Thefuel cell system according to claim 2, wherein the flow control meansstarts the flow of the refrigerant in the exhaust heat utilization lineafter starting the flow of the refrigerant in the cooling line whenstarting-up the fuel cell.
 7. The fuel cell system according to claim 6,further comprising: timer means for measuring time from a stop of thefuel cell to the next start-up, wherein the flow control means variesstart time, at which the flow of the refrigerant in the exhaust heatutilization line is begun at the start-up of the fuel cell, based on thetimer means.
 8. The fuel cell system according to claim 6, furthercomprising: a temperature sensor for detecting the temperature of therefrigerant, wherein the flow control means varies start time, at whichthe flow of the refrigerant in the exhaust heat utilization line isbegun at the start-up of the fuel cell, based on the temperature sensor.9. The fuel cell system according to claim 2, wherein the flow controlmeans causes the refrigerant to flow in at least one of the cooling lineand the exhaust heat utilization line during an intermittent operationof the fuel cell.
 10. The fuel cell system according to claim 9, whereinthe flow control means starts the flow of the refrigerant in the coolingline before the flow of the refrigerant in the exhaust heat utilizationline during the intermittent operation of the fuel cell.
 11. The fuelcell system according to claim 2, wherein the flow control means stopsthe flow in the exhaust heat utilization line before the flow of therefrigerant in the cooling line when the fuel cell is stopped.
 12. Thefuel cell system according to claim 2, wherein the flow control meanscomprises: a cooling pump for pressure-feeding the refrigerant in thecooling line; an exhaust heat utilization pump for pressure-feeding therefrigerant in the exhaust heat utilization line; and control means forcontrolling the driving of the cooling pump and the exhaust heatutilization pump, wherein the control means starts the driving of thecooling pump and then starts the driving of the exhaust heat utilizationpump.
 13. The fuel cell system according to claim 12, wherein thecontrol means carries out flow rate control such that the flow rate ofthe refrigerant by the cooling pump is larger than the flow rate of therefrigerant by the exhaust heat utilization pump.
 14. The fuel cellsystem according to claim 12, further comprising: a temperature sensorfor detecting the temperature of the refrigerant, wherein the controlmeans controls the driving both of the cooling pump and the exhaust heatutilization pump based on the temperature sensor.
 15. The fuel cellsystem according to claim 12, wherein the exhaust heat utilization lineis connected to a point of branching from and a point of merging withthe cooling line at a refrigerant outlet side of the fuel cell, and acheck valve is further provided on the cooling line on the upstream sidebeyond the point of merging to block the flow of the refrigerant fromthe point of merging to the refrigerant outlet of the fuel cell.
 16. Thefuel cell system according to claim 2, wherein the flow control meanscomprises: a single pump for pressure-feeding the refrigerant in thecooling line and the exhaust heat utilization line; and control meansfor controlling the driving of the pump, wherein the cooling line hasthe passage resistance set to be lower than that of the exhaust heatutilization line, so that the refrigerant of the cooling line starts toflow into the fuel cell before the refrigerant of the exhaust heatutilization line.
 17. The fuel cell system according to claim 2, whereinthe flow control means comprises: a single pump for pressure-feeding therefrigerant in the cooling line and the exhaust heat utilization line; aswitching valve for switching the flow of the refrigerants of thecooling line and the exhaust heat utilization line to the fuel cell; andcontrol means for controlling the driving of the pump and the switchingvalve, wherein, when starting the flow of the refrigerant of the exhaustheat utilization line to the fuel cell, the control means changes theswitching valve over to the cooling line to start the flow of therefrigerant of the cooling line to the fuel cell.
 18. The fuel cellsystem according to claim 2, wherein the cooling line and the exhaustheat utilization line include a confluence for merging the refrigerantat a refrigerant inlet side of the fuel cell and also include a branchpoint for branching the refrigerant at a refrigerant outlet side of thefuel cell.
 19. A fuel cell system which circulates a refrigerant flowingin a fuel cell to cool the fuel cell and which is capable of heatingair-conditioning gas in an air-conditioning line by exhaust heat of therefrigerant that has passed through the fuel cell, the fuel cell systemcomprising: a cooling line which has a first heat exchanger for coolingthe refrigerant and circulates the refrigerant to the fuel cell; anexhaust heat utilization line which has a second heat exchanger forheat-exchanging the refrigerant with the air-conditioning gas in theair-conditioning line and which circulates the refrigerant to the fuelcell; and flow control means for controlling the flow of the refrigerantin the cooling line and the exhaust heat utilization line, wherein theflow control means carries out flow rate control such that the flow rateof the refrigerant of the cooling line is larger than that of theexhaust heat utilization line when the refrigerants of the cooling lineand the exhaust heat utilization line are merged and passed through thefuel cell.
 20. A fuel cell system which circulates the refrigerantflowing in a fuel cell to cool the fuel cell and which is capable ofheating air-conditioning gas in an air-conditioning line by exhaust heatof the refrigerant that has passed through the fuel cell, the fuel cellsystem comprising: a cooling line which has a first heat exchanger forcooling the refrigerant and circulates the refrigerant to the fuel cell;an exhaust heat utilization line which has a second heat exchanger forheat-exchanging the refrigerant with the air-conditioning gas in theair-conditioning line and which merges with the cooling line at arefrigerant inlet side of the fuel cell and branches from the coolingline at a refrigerant outlet side of the fuel cell; a bypass linethrough which the refrigerant flows to bypass the fuel cell; and flowcontrol means for controlling the flow of the refrigerant in the coolingline, the exhaust heat utilization line, and the bypass line, whereinthe flow control means causes the refrigerant to flow in the bypass lineand mixes the refrigerants of the cooling line and the exhaust heatutilization line, then circulates the refrigerant to the fuel cell,shutting off the flow of the refrigerant in the bypass line.
 21. Acooling apparatus for a fuel cell, comprising: a heat exchanger forcooling a refrigerant; a circulation passage through which therefrigerant is circulated between the heat exchanger and the fuel cellby a pump; a bypass passage through which the refrigerant in thecirculation passage is supplied to the fuel cell to bypass the heatexchanger; a fluidic valve for setting the flow of the refrigerant tothe heat exchanger and the bypass passage; and control means forcontrolling the fluidic valve and the pump, wherein, when starting upthe fuel cell, the control means causes the driving of the pump to bestarted after the opening degree of the fluidic valve is changed from aninitial opening degree, which is an opening degree before the start-up,to a predetermined opening degree.
 22. The cooling apparatus for a fuelcell according to claim 21, further comprising a temperature sensor fordetecting the temperature of the refrigerant, wherein the control meanssets the fluidic valve to the predetermined opening degree based on thetemperature sensor when starting-up the fuel cell.
 23. The coolingapparatus for a fuel cell according to claim 22, wherein a plurality ofthe temperature sensors are provided on the circulation passage and thebypass passage, and the control means sets the fluidic valve to thepredetermined opening degree based on the plurality of temperaturesensors when starting-up the fuel cell.
 24. The cooling apparatus for afuel cell according to claim 21, further comprising: a first temperaturesensor for detecting the temperature of the refrigerant in the fuelcell; and a second temperature sensor for detecting the temperature ofthe refrigerant in the heat exchanger, wherein the control means setsthe fluidic valve to the predetermined opening degree based on thetemperature difference between the first and second temperature sensorswhen starting-up the fuel cell.
 25. The cooling apparatus for a fuelcell according to claim 24, wherein the control means sets an openingdegree, as the predetermined opening degree of the fluidic valve, suchthat the fluidic valve blocks the flow of the refrigerant into the heatexchanger while allowing the refrigerant to flow into the bypass passageif the temperature difference is a threshold value or more.
 26. Thecooling apparatus for a fuel cell according to claim 25, wherein thepredetermined opening degree is an opening degree at which the fluidicvalve is fully opened to the bypass passage, and the control meansstarts the driving of the pump after a zero point adjustment for placingthe fluidic valve in the fully opened state when starting up the fuelcell.
 27. The cooling apparatus for a fuel cell according to claim 21,wherein the predetermined opening degree is an opening degree at whichthe fluidic valve allows the refrigerant to flow into at least thebypass passage.
 28. The cooling apparatus for a fuel cell according toclaim 27, wherein the predetermined opening degree is an opening degreeat which the fluidic valve is fully opened to the heat exchanger. 29.The cooling apparatus for a fuel cell according to claim 27, wherein thepredetermined opening degree is an opening degree at which the fluidicvalve is fully opened to the bypass passage, and the control meansstarts the driving of the pump after a zero point adjustment for placingthe fluidic valve in the fully opened state when starting up the fuelcell.
 30. The cooling apparatus for a fuel cell according to claim 27,wherein, when starting-up the fuel cell, the control means changes thefluidic valve to the predetermined opening degree after the zero pointadjustment of the fluidic valve at the initial opening degree.
 31. Thecooling apparatus for a fuel cell according to claim 30, wherein thecontrol means sets the fluidic valve to be fully opened to the bypasspassage, as the zero point adjustment of the fluidic valve.
 32. Thecooling apparatus for a fuel cell according to claim 30, wherein thecontrol means sets the fluidic valve to be fully opened to the heatexchanger, as the zero point adjustment of the fluidic valve.
 33. Thecooling apparatus for a fuel cell according to claim 21, wherein theinitial opening degree is an opening degree at which the fluidic valveallows the refrigerant to flow into the heat exchanger.
 34. The coolingapparatus for a fuel cell according to claim 21, wherein the initialopening degree is an opening degree at which the fluidic valve allowsthe refrigerant to flow into the bypass passage.
 35. The coolingapparatus for a fuel cell according to claim 21, wherein the initialopening degree is an opening degree at which the fluidic valve allowsthe refrigerant to flow into both the heat exchanger and the bypasspassage.
 36. The cooling apparatus for a fuel cell according to claim21, wherein the control means sets the fluidic valve to the initialopening degree when stopping the fuel cell.
 37. A cooling apparatus fora fuel cell, comprising: a heat exchanger for cooling a refrigerant; acirculation passage through which the refrigerant is circulated betweenthe heat exchanger and the fuel cell by a pump; a bypass passage throughwhich the refrigerant in the circulation passage is supplied to the fuelcell to bypass the heat exchanger; a fluidic valve for setting the flowof the refrigerant to the heat exchanger and the bypass passage; andcontrol means for controlling the fluidic valve and the pump, wherein,when starting-up the fuel cell, the control means stops the driving ofthe pump and then sets the fluidic valve to a predetermined initialopening degree.
 38. The cooling apparatus for a fuel cell according toclaim 37, wherein the initial opening degree is an opening degree atwhich the fluidic valve allows the refrigerant to flow into the heatexchanger.
 39. The cooling apparatus for a fuel cell according to claim37, wherein, when starting-up the fuel cell, the control means startsthe driving of the pump after changing the fluidic valve from theinitial opening degree to a predetermined opening degree.
 40. A coolingapparatus for a fuel cell, comprising: a heat exchanger for cooling arefrigerant; a circulation passage through which the refrigerant iscirculated between the heat exchanger and the fuel cell by a pump; abypass passage through which the refrigerant in the circulation passageis supplied to the fuel cell, bypassing the heat exchanger; a fluidicvalve for setting the flow of the refrigerant to the heat exchanger andthe bypass passage; and control means for controlling the fluidic valveand the pump, wherein, when starting-up the fuel cell, the control meanscarries out zero point adjustment on the fluidic valve and also changesthe opening degree after the zero point adjustment to a predeterminedopening degree before starting the driving of the pump.
 41. The coolingapparatus for a fuel cell according to claim 21, wherein the fluidicvalve is a rotary valve.